Mechanisms for Optical Limiting

Mechanisms for Optical Limiting Chapter 2 2.1. Reverse Saturable Absorption In the mid 1960s shortly after the invention of the laser, many researchers were investigating dyes for potential application to Q-switching of the laser cavity. For this application, dyes were sought that would bleach to transparency under intense illumination (saturable absorbers). Guiliano and Hess [2a] in 1967 were investigating vat dyes and their modified cousins and noted some examples that not only did not bleach to transparency but instead darkened at high intensities. This was the first recognition of the property of reverse saturable absorption (RSA). Reverse saturable absorption generally arises in a molecular system when the excited state absorption cross section is larger than the ground state cross section. The process can be understood by considering a system that is modeled using three vibronically broadened electronic energy levels, as shown in figure 2.1. The cross section for absorption from the ground state 1 is à ¯Ã‚ Ã‚ ³1. à ¯Ã‚ Ã‚ ³2 is the cross section for absorption from the first excited state 2 to the second excited state 3. The lifetime of the first excited state is à ¯Ã‚ Ã‚ ´2 (seconds). Figure 2.1: Three level and Four level models for RSA As light is absorbed by the material, the first excited state begins to become populated and contributes to the total absorption cross section. If à ¯Ã‚ Ã‚ ³2 is smaller than à ¯Ã‚ Ã‚ ³1, then the material becomes more transparent or ‘bleaches’ i.e. it is a saturable absorber. If à ¯Ã‚ Ã‚ ³2 is larger than à ¯Ã‚ Ã‚ ³1, then the total absorption increases, and the material is known as a reverse saturable absorber. This behavior is shown in figure 2.2 Figure 2.2: Plot of the incident intensity versus the transmitted intensity of a typical three level RSA material. The change in intensity of a beam as it propagates through the material is: , (2.1) Where z is the direction traversed, NT is the total number of active molecules per area in the slice dz, N2 is the population of level 2 and the population of level 3 has been neglected. Initially, the material obeys Beer’s law when 2 is unpopulated, and the transmission is constant as the incident fluence is increased. The slope is given by. At a sufficiently high fluence, however, the first excited state 2 becomes substantially populated and in the limit of complete ground state depletion the slope again becomes constant at the new value of. The optical limiting action is not truly limiting, as the fluence, which is transmitted, is still increasing with increasing incident fluence, but it does so more slowly. If the ratio à ¯Ã‚ Ã‚ ³2/à ¯Ã‚ Ã‚ ³1, is sufficiently large, however, the new transmission will be small and in a properly designed system the dynamic range of the sensor will be greatly extended. The three level diagrams describe the simplest case for RSA materials but can generally only be applied for subnanosecond pulses and under circumstances such that transitions from the second excited state are negligible. The energy states involved in three level materials usually consists of singlet states and the transitions are all allowed. The transition cross sections are therefore large, but a disadvantage is that de-excitation is rapid (à ¯Ã‚ Ã‚ ´2 is small). This necessitates larger intensities for long pulses to activate the nonlinearity through populating the excited electronic state. Fortunately, on longer timescales in some systems, significant intersystem crossing to other states can occur from the first excited state. In this case the five level diagrams shown in figure 2.1 is applicable. The excited state 4 is usually a triplet or other long-lived state, and for long pulses it can act as a metastable state that accumulates population during the pulse. The lifetime of 4 gives an indication of the maximum pulse width for which the material is efficient to act as an optical limiter. Pulses with duration longer than the metastable state allow some of the metastable molecules generated by the leading edge of the pulse to decay to the ground state before the trailing edge have passed, thereby reducing the RSA. In most systems, à ¯Ã‚ Ã‚ ´3 and à ¯Ã‚ Ã‚ ´5 are very small and significant populations of 3 and 5 do not accumulate. Therefore, N3 and N5 can be set to zero, considerably simplifying the dynamical equations describing. The equations representing the full five level models are given below by: (2.2) (2.3) (2.4) (2.5) (2.6) (2.7) and (2.8) Where hà ¯Ã‚ Ã‚ ® is the energy per photon, I is the intensity of the pulse and stimulated emission has been neglected. The latter assumes that optical coupling to the excited states is well above the bottom of the vibronic manifolds and that relaxation from the optically-coupled states to the bottom of the manifolds occurs on a time scale that is much shorter than the pulse duration. To completely understand the response of an RSA device, these equations must be solved as the pulse propagates through the material. The material parameters necessary to solve the equations are à ¯Ã‚ Ã‚ ³1, à ¯Ã‚ Ã‚ ³2, à ¯Ã‚ Ã‚ ³4, à ¯Ã‚ Ã‚ ´2, à ¯Ã‚ Ã‚ ´4 and à ¯Ã‚ Ã‚ ´24. For optimum optical limiting performance, certain parameters need to be maximized. The ratio of the excited state absorption to the ground state, à ¯Ã‚ Ã‚ ³2/à ¯Ã‚ Ã‚ ³1, à ¯Ã‚ Ã‚ ³4/à ¯Ã‚ Ã‚ ³1 should be large to minimize the transmission of the limiter at high incident intensity. For maximum efficiency, the lifetime of the triplet state (à ¯Ã‚ Ã‚ ´2) and the intersystem crossing rate l/à ¯Ã‚ Ã‚ ´24 should be large to populate the triplet state and maintain the population throughout the pulse. By the mechanism of RSA we get better performance on optical limiting. 2.2. Two-Photon Absorption (TPA): Two-photon absorption (TPA) can also be used in a manner similar to RSA to construct optical limiters. In contrast with reverse saturable absorption, TPA is an instantaneous nonlinearity that involves the absorption of photon from the field to promote an electron from its initial state to a virtual intermediate state, followed by the absorption of a second photon that takes the electron to its final state. Since the intermediate state for such transitions is virtual, energy need not be conserved in the intermediate state but only in the final state. The mechanism of TPA can be thought of in terms of the three level RSA model for the case where the lifetime of the intermediate state approaches zero and the ground state absorption is extremely low (highly transparent). The intensity of the beam as it traverses the material is: (2.9) Where z is the linear absorption coefficient and à ¯Ã‚ Ã‚ ¢ is the TPA coefficient which is related to the imaginary part of à ¯Ã‚ Ã‚ £(3) by the equation (SI units): (2.10) Here, à ¯Ã‚ Ã‚ · is the circular frequency of the optical field, n0 is the linear index of refraction, and c is the speed of light in vacuum. The solution to the propagation equation for à ¯Ã‚ Ã‚ ¡= 0 (transparent material at low intensities) is given by (2.11) Where L is the sample length. This clearly demonstrates that the output intensity decreases as the input intensity increases, exactly the behavior that is desired for an optical limiter. The strength of this reduction is explicitly dependent on the TPA coefficient, the incident intensity and the sample thickness. For TPA, the material response is of the order of an optical cycle and is, therefore, independent of the optical pulse length for a fixed intensity. The device will respond virtually instantaneously to the pulse. On the other hand, because of the limited magnitude of à ¯Ã‚ Ã‚ ¢ in existing materials, high intensities are required to realize significant TPA. Since the intensity is essentially the energy density divided by the pulse duration, short pulses are required to achieve limiting with TPA for energy densities that may be high enough to damage an optical sensor. 2.3. Free-Carrier Absorption: This type of limiting occurs in semiconductor materials. Once carriers are optically generated in a semiconductor, whether by single photon or two-photon absorption, these electrons (holes) can be promoted to states higher (lower) in the conduction (valence) band by absorbing additional photons. This process is often phonon assisted, although depending on the details of the band structure and the frequency of the optical excitation, it may also be direct. The phonon assisted phenomenon is referred to as free-carrier absorption, and it is analogous to excited-state absorption in a molecular system. It is clearly an accumulative nonlinearity, since it depends on the buildup of carrier population in the bands as the incident optical pulse energy is absorbed. Free-carrier absorption always plays some role in the operation of a semiconductor limiter, if the excitation process results in the generation of significant free carrier populations in the bands. While it certainly contributes to the limiter performance and its inclusion is important in the precise modeling of the response of such devices, just as in the case of TPA, its importance typically pales in comparison with nonlinear refractive effects, whether the carriers are generated by single photon or two photon transitions. 2.4. Nonlinear Refraction Optical limiters based on self focusing and defocusing form another class of promising devices. The mechanism for these devices may arise from nonlinear refraction associated with carrier generation by either linear or two photon absorption in a semiconductor. Both self focusing and defocusing devices operate by refracting light away from the sensor as opposed to simply absorbing the incident radiation. Compared to strictly absorbing devices, these limiters can, therefore, potentially yield a larger dynamic range before damage to the limiter itself. Figure 2.3 (a) shows the typical device configuration for a self defocusing limiter, while figure 2.3 (b) shows a similar device based on self focusing. A converging lens is used to focus the incident radiation so it passes through the nonlinear medium. This lens provides optical gain to the system, allowing the device to activate at low incident intensities. The output passes through an aperture before impinging on the detector. At low input levels, the nonlinear medium has little effect on the incident beam, and the aperture blocks an insignificant portion of the beam, thus allowing for a low insertion loss for the device. When nonlinear refraction occurs, however, the nonuniform beam profile within the medium results in the generation of a spatially nonuniform refractive index. This acts as either a negative or positive lens, depending on the sign of the refractive nonlinearity, causing the incident beam to either defocus or focus. Figure 2.3: (a) Typical self defocusing optical limiter configuration (b) Typical self focusing optical limiter configuration. In a properly designed system, this self lensing results in significant energy blocked by the system aperture, thereby protecting the sensor. The location of the nonlinear medium is critical to the operation of the refractive limiting device. A self-focusing limiter works best if the nonlinear medium is placed approximately a Rayleigh range before the intermediate focus of the device. When the focusing lens is induced the effective focal length of the device is reduced, and hence a larger beam appears at the exit aperture. For a self-defocusing material, the optimum geometry is approximately one Rayleigh range after the focus. This geometry dependence can be exploited to determine not only the sign of the nonlinear refraction in a given medium, but the magnitude as well. This is the principle behind the so-called Z-scan technique, which has been pioneered by Van Stryland and coworkers [2b,2c]. The technique consists of moving the nonlinear medium through the focal region of a tightly focused beam while measuring the transmittance through an aperture placed in the far field of the focal plane. When the medium is far before the focal plane, no self-lensing occurs. As the medium approaches the focal plane, the high intensity begins to induce a lens in the medium. For a negative nonlinearity, this lens tends to collimate the beam, thereby increasing the transmittance through the aperture. Near the focal plane, even though the intensity is highest, the influence of the induced lens is minimized, resulting in a transmittance comparable to the linear transmittance. This is similar to placing a thin lens at the focus of a beam; this results in minimal effect on the far field beam pattern. As the sample is moved beyond the focal plane, the negative lens tends to increase the beam divergence, resulting in a decrease in the aperture transmittance. As the medium is moved still farther from focus, the intensity again becomes weak enough that the induced lensing is negligible. This sequence results in a change in transmittance with a characteristic peak, followed by a null, followed by a valley as the sample is moved from the input lens, through focus, toward the output lens. For a positive nonlinearity, the pattern consists of a valley, a null, and then a peak. Thus, the sign of the nonlinearity is readily determined. While nonlinear absorption has been neglected in this discussion, if present, it must also be accounted for. This is readily done by removing the aperture in the limiter and collecting all the light transmitted by the nonlinear material. This measurement is then insensitive to nonlinear refraction. The response in this case is a valley symmetrically located about the focal plane. It should be noted that nonlinear absorption and induced scattering cannot be distinguished by this technique. The general shape of the Z-scan for a positive index change, negative index change, and a nonlinear absorber or scatterer is shown in figure 2.4 . Figure 2.4: Schematic representation of z-scan results for a negative refractive nonlinearity (dashed curve) and a positive refractive nonlinearity (dotted curve). Both curves have been corrected for absorption. The solid curve shows the result of removing the aperture from the measurement apparatus and collecting all the transmitted light, thus isolating the nonlinear absorption [1e]. 2.5. Induced Scattering Scattering roots from interaction of light with small centers which may be physical particles or simple interfaces sandwiched between non-excited and excited molecular groups. The size of the scattering centers determines whether the scattering will be quite directional or reasonably uniform. Transmission of a medium, for a given solid angle, decreases when scattering centers are induced in the medium by an optical signal. Therefore, this phenomenon of scattering induced by optical signal may be applied to manufacture of optical limiters for sensor protection. Optical limiters based on induced scattering are usually focused on liquid media, as the phenomenon is usually reversible in these media. That is to say, the liquid in the excited state can return to equilibrium with ease in the absence of chemical or structural decomposition. However, in solids, usually irreversible decomposition processes generate the scattering centers which can lead to degradation in the device’s lin ear operation. When light is incident on a particle, the electric charges within the particle oscillate due to its interaction with the electric field. Radiations are then caused by the oscillation. In 1899, Lord Rayleigh originally presented the analytic expression and theory of the elastic scattering of light from particles with dimensions smaller than the wavelength of light. Rayleigh scattering is the name given to the phenomenon. This applies only to particles whose dimensions are quite smaller than the wavelength of light or which are non-absorbing. However, in 1908, Mie developed a theory for particles with dimensions comparable to the wavelength of light or greater [2d]. The transmitted intensity equations of the Mie scattering are notably more intricate than of Rayleigh scattering. In Mie scattering, a bigger percentage of the scattered radiation is in forward direction as the size of the scattering particles increases, implying that limiting based on Mie scattering will not be as effectiv e as Rayleigh scattering. 2.6. Photorefraction Two devices, namely coherent-beam excisor and the beam fanning limiter based on the photorefractive effect are used to limit coherent optical radiation. Materials showing photorefraction should have a nonzero χ(2). The traditional photorefractive mechanism is based on the photorefractive crystal which possesses deep levels that can be excited optically to generate free charge in the conduction or valence band. In a material showing photorefraction, when two coherent beams interfere, additional mobile charge are generated at the peaks of the intensity pattern than at the valleys through photoexcitation of the deep levels of the crsytal. These charges which are photoexcited at the peaks diffuse into the valleys ensuing a variation of charge spatially, in correspondence to the material’s interference pattern. These charges results in an electrostatic space-charge field which gives rise to a change in refractive index through the electro-optic effect in a properly oriented cry stal. Energy coupling and energy exchange can then be achieved between the two beams through the grating generated, which is 90 degrees phase shifted from the intensity of the photon field. A high intensity coherent beam when incident singly on a photorefractive crystal, the energy can be coupled into a large amount of low intensity scattered beams. Fields with new wave vectors are generated inside the crystal by the scattering of the incident beam at the crystal imperfections. The photorefractive gratings are then produced by the interference of the incident field with these scattered fields. Optical signal can later be coupled from the incident beam to the scattered beams through diffraction from these gratings. The light gets preferentially scattered to one side of the crystal as there is a preferred direction of energy transfer for photorefractive gratings which is determined by the direction of the c-axis of the crystal and the charge carriers’ sign. This photorefractive beam fanning phenomenon can be quite efficient in reducing the intensity of the transmitted beam. Construction of an optical limiter using this beam fanning process has been demonstrated by Cronin-Golomb and Yariv [2e]. The photorefractive excisor is another device which provides a weak seed beam to interfere with the incident beam. It is assembled to protect the sensor in such a way that the photorefractive grating produced by the interference of the primary beam with the seed beam at high intensities couples energy from the strong incident beam to the weak seed beam. The speed and efficiency of the device is thus improved. 2.7. Summary All of the nonlinear phenomena discussed above can be used for optical limiting, and figure 2.5 schematically illustrates the application of some of these processes. Figure 2.5 (a) depicts the use of induced absorption, such as reverse saturable absorption, two-photon absorption, and free-carrier absorption. Figures 2.5(b) and 2.5(d) represent, respectively, a self-defocusing limiter, self-focusing limiter, and an induced scattering limiter. Finally, figures 2.5(e) and 2.5(f) illustrate a photorefractive beam fanning limiter and a photorefractive excisor device. While it is often the case that any given material will exhibit multiple nonlinear properties, for simplicity the effects of each individual process have been separately depicted in figure 2.5. Figure 2.5: Some optical limiters based on different mechanisms (a) an induced absorption limiter (b) Self defocusing limiter (c) Self focusing limiter (d) Induced scattering limiter (e) Beam fanning limiter (f) Photorefractive excisor device [1e].

The History of Oppressed Puerto Rico :: Historical Spanish Essays

The History of Oppressed Puerto Rico Jesus Colon, in â€Å"How to Know the Puerto Ricans,† makes a statement that I believe explains and articulates the effect centuries of exploitation has had on Puerto Rico, and on the identity of Puerto Ricans. He writes, â€Å"So when you come to knock at the door of a Puerto Rican home you will be encountered by this feeling in the Puerto Rican-sometimes unconscious in himself-of having been taken for a ride for centuries.†(Santiago, 71) This assertion is appropriate and logical in the sense that Puerto Rico was invaded, ruled, and exploited by the Spaniards from 1508 until July 1898 when the Spanish flag was lowered and the United States began its invasion. With the exclusion of the aristocrats, who were either directly from Spain or criollos , there was complete oppression in Puerto Rico during the time it was a Spanish colony. The history of Puerto Rico under Spanish rule is useful in understanding the formation of Puerto Rican identity and in understanding some of the literature written by Puerto Ricans regarding issues of identity. The numerous historical, economical, social, and political circumstances of Puerto Rico as a colony has affected identity formation of its people. In 1508, Ponce de Leon led the arrival of Spanish into Puerto Rico. Between the years of 1511-1513, Taà ­nos fought against the Spaniards because they were taking away the Taà ­no culture. An outright rebellion with guerrilla warfare occurred in 1511 and then 1513-1514 experienced a lessening of this overt manner of rebellion and a conversion to more evasive and passive forms of resistance (Figueroa, Sept. 22). Among Puerto Ricans, especially the jibaros , there was a great amount of anti-state, anti-Spanish sentiment. However, the plebian peasantry (jibaros) erected a faà §ade that they were following Spanish authorities' orders, although in reality the peasants discounted and discredited the orders of the Spaniards (Figueroa, Sept. 22). By presenting this faà §ade, the authorities falsely believed that the peasantry was not going to cause problems and would be loyal to Spain and its delegates. From 1650 until 100 years later, â€Å"relative isolation from the international economy fostered the growth of an independent, racially mixed peasantry whose contact with the outside world was limited to occasional contraband trade with foreigners.†(Scarano, 4) Despite evidence that it would be unsuccessful, the Spanish government tried to create a plantation labor force from the peasantry. This would

The Different Styles of Narration

Narrators in Film and Novel In this chapter, Stam introduces the different styles of narrators in Novel. According to him, they vary from the first-person report-narrator to the multiple letter writers of epistolary novels, to outside-observer narrators of reflexive novels like Don Quixote and Tom Jones, to the once intimate and impersonal narrator of Madame Bovary, to the â€Å"stream-of-consciousness† narrators, on to the intensely objective/subjective obsessional narrators of Robbe-Grillet.What interests Stam is the fact that these different styles of narration cannot be really explained by the conventional terms that exist. That happens because language and grammar are the foundation of the traditional analysis of film and literature and in this context have leaded to a terminology based on them, a terminology such as first-person narrator or third-person narrator. This kind of grammar based terminology and approach, can create confusion and obscure facts like writers shif ting person and changing the relation between narrator and fiction.For Stam though, the most important issue is not the grammatical â€Å"person† as he says, but the control an author has over the intimacy and the distance and how he calibrates the access to a character’s knowledge and consciousness. Literary narration can be complicated through film because of the verbal narration (voice over/speech of characters) and the capacity a film has to present the different appearances of the world.Andre Goudreault says that filmic narration is more powerful than â€Å"monstration† (showing) and â€Å"narration† (telling) and that for him, editing and other cinematic procedures consist of the evaluation and the comments of the filmic narrator. This way films tell stories (narrate) and at the same time stage them (show). Stam explains that  «the film as â€Å"narrator† is not a person (the director) or a character in the fiction but, rather, the abstract instance of a superordinate agency that regulates the spectator’s knowledge ».In other words â€Å"le grand imagier† and the â€Å"meganarrator†, all names attributed to the narrator, can be considered as the conductor of an orchestra who uses the instruments of cinematic expression as musical instruments. The author (Stam) continues his chapter by explaining how a double play of forms can be made possible through sound cinema. Voice-over narration and monstration (showing) mutually reinforce each other like in Sunset Boulevard where the scene is supposed to be a visual manifestation of what Joe Gillis is saying. We will also come across that during my extract analysis.In more modernist films like India Song (1975) and Last year at Marienbad (1961) the two forms contradict each other, in a sense that what is told is not what is being shown. Since sound made its appearance in film, cinema has been as Chion says â€Å"vococentric†, it has an orientation toward the human voice, which, in the cinema, according to Stam can provide information and focus for spectatorial identification. A debate has started about whether a film can actually narrate. Film theorists believe that filmic â€Å"narration† is only a fiction of the human mind.They don’t argue of course about films being able to develop certain processes of â€Å"narration† but they state that these processes can only be considered as cheap copies of a â€Å"narrator†. This logic though can also be valid for novelistic narrators. Theorist like Christian Metz, consider film to be a deployment of â€Å"impersonal† narration in which case the narrator is both the one that provides the fictional world and the one that comments on this same world. Stam chooses to stand on another important matter of narratology, the relationship between the events told and the temporal standpoint of the telling.For example, whether the telling if the story is takin g place after the events of the story, which is called a retrospective narration, or prior, in which case, as he explains, we have an oracular or prophetic narration. In some cases, the telling and the events are simultaneous or even interpolated, meaning that they take place during the intervals between the moments of the main action. For Stam, the question is how all these different settings of time manage to be translated within adaptations. There is the case of â€Å"embedded narration†, where a story contains another story inside it, in a narrative mise-en-abyme.This is the case of the extract I have chosen to analyze. These substories go by the term of hypodiegesis. This occurs when a story contains a sub-story. For Genette, the term â€Å"diegesis† refers to three things, the time and space, the participants, and the events in a narrative. Around this term he creates terms such as â€Å"autodiegetic† (when the narrator generates and tells his own story), â€Å"homodiegetic† (when the narrator is part of the story but is not the protagonist) and â€Å"heterodiegetic† (when the narrator is not part of the story at all). â€Å"Autodiegetic† comes from the greek word â€Å" †, â€Å"homodiegetic† from â€Å" and â€Å"heterodiegetic† from â€Å" †. â€Å" † means â€Å"narrative† and â€Å" † has the meaning of â€Å"itself†. â€Å" †means it has a resemblance with something and â€Å" † that it is something different. So when the narrator is autodiegetic it means he is narrating himself, when he is homodiegetic, he narrating about something similar with him and when he is heterodiegetic he is narrating about something different that him. Stam adds that the narrator can be single or collective, a group narrator and that off screen narrators can be single, multiple or even contradictory like in the case of Citizen Kane.He also makes a distinction between living and dead narrators. A dead narrator would be when at the time the narrator is talking it has been known to us that he is already dead in the story. So the narration would probably take place after the events. Stam continues his analysis by referring to reliability. Narrators can be completely suspect (like Leonard in Memento, the movie I have chosen to analyze) ,more or less reliable, or serve as dramatized spokespersons for the implied author. The modern period has a taste for changing narrators and unreliable ones.This is the case of the bildungsroman, a literary genre that focuses on the psychological and moral growth of the protagonist from youth to adulthood and in which character change is extremely important. Sometimes, also, the reliability of a narrator as the governess in James’s Turn of the Screw can cause difficulty for literary interpretation. Cases of â€Å"lying narration† are also offered in the cinema. What is challenging for Stam, is to find a way to reproduce in a way all the ambiguity and readerly decipherment of the text, on a cinematic register.Self-obsessed neurotic narrators like Humbert Humbert in Lolita, tend to be relativized by adaptation in a severe manner. While the narrator in the novel is â€Å"autodiegetic†, in the film he switches to â€Å"homodiegetic†. The problem is that the discursive power an unreliable narrator possesses is drastically reduced by film because of the multitrack nature of the film. In a novel, there is only one track available and that is the verbal track, which is of course controlled by the narrator.In a film though, even if the narrator can partially control the verbal track by the use of voice-over or character dialogue, that same control remains subject to a great amount of constraints such as the presence of other characters, voices, objects etc. While it’s not impossible to portrait an unreliable first-person narration in the cinema, all the problems mentioned above lead us to understand that it would be extremely difficult and could only be succeeded by relentless subjectification in almost all the cinematic registers.Point of View This chapter of â€Å"The Theory and Practice of Adaptation† tries to answer questions concerning focalization and point of view which is a term that has been regarded as problematic. â€Å"Point of view† can either refer to an ideological orientation, an emotional stance or even to the angle from which a story is told. Unlike literature, this term in cinema is always literal because of the camera set-ups that are required. Nevertheless, it can be figurative too at the same time, through the use of cinematic means.For Stam, an authorial point of view can be sensed in films. He explains that the film’s multitrack and multiform nature are to be seriously considered if we want to understand the cinematic point of view since each and every filmic track and procedure can convey one. Next, Stam takes interest in the relationship between the knowledge of the character and that of the narrator, something that has been referred to as â€Å"focalization†. According to Todorov, three were the possibilities: narrators could either know more, less or as much as the characters.Of course, one might argue that quantity is not always the case, since the two can also know differently. Gennete chooses to make a distinction between narration (who speaks or tells) and focalization (who sees) and then separates this last term into three sub-terms. â€Å"Zero focalization† refers to narrators who know much more than the rest of the characters. â€Å"Internal focalization† occurs when events are filtered through a character and is subdivided into â€Å"fixed† for when it is limited to a single character or â€Å"variable† for when it’s passed from character to character.Finally, â€Å"external focalization† takes place when the rea der cannot access to point of view and motivations and can only be a simple observer of external behavior. Andre Goudrault and Francois Jost argued that the term of focalization can create problems when it comes to the visual medium of cinema since the sound film has the ability to show what a character sees and say what he thinks at the same time. They proposed a separation of these two functions by the use of two terms. The first term is â€Å"ocularization† and refers to the relation of what the camera shows and what the character is supposed to be seeing. Focalization† was used by the two narratologists to characterize the cognitive point of view adopted by the story. Stam also examines how â€Å"point of view† intersects with â€Å"style†. Adaptations have been considered less modernist than their sources but that is not the case with adaptations like the one of Virginia Woolf’s Orlando by Sally Potter in 1992 or Bunuel’s That Obscure Ob ject of Desire, where, in the contrary, the novel’s modernism is amplified. The author chooses to conclude this chapter not by answering questions, but rather by asking them.He is interested in the handling of temporality and wonders if instances of Genette’s â€Å"pause† take place in the novel and the adaptation, as montage sequences or as static close shots without action. He mentions Cristian Metz’s eight syntagmatic types in the cinema (one-shot sequence or autonomous shot, parallel syntagma, bracket syntagma, descriptive syntagma, alterning syntagma, scence, episodic sequence, ordinary sequence) and asks how these types are useful and wonders about the existence of any correlations with temporality in film and their nature.He questions the role of description in novel and film and wants to know if there is a possibility of pure (unnarrativized) description in any of these two mediums and finally sets the question of stylistic equivalences across the m. MEMENTO [pic] Memento is a film directed by Christopher Nolan and released in the year 2000. He wrote the story with his brother Jonathan Nolan, based on a short story published by Jonathan called Memento Mori. The whole film can be divided in 22 colored and 22 black and white sequences plus the opening sequence which runs backward and is shown in slow motion.In order to understand the analysis of the sequence chosen (1. 22. 58 – 1. 48. 43) a brief introduction to the movie’s plot is necessary: Leonard Shelby (Guy Pearce) is a former insurance investigator whose wife was killed during an assault in their home. During that assault he sustained a head trauma and now suffers from a memory dysfunction which makes him unable to create any new memories after the incident. He remembers of everything prior the incident though like who he is, what his job was and everything about his life with his wife.But each time he wakes up he can’t remember where he is, why he is there or what he did and who he met the day before. He cannot trust anyone and his whole life is one big constant puzzle solving. There is only one thing that motivates him and that is to hunt down and kill his wife murderer. To collect the facts needed to avenge his wife he has developed a strategy that consists of taking polaroid pictures of everyone he meets, of the place he lives in and so on while also getting tattooed on his body every important information he comes across. pic]Leonard’s tattooed body In his investigation he is helped by two persons, Teddy (Joe Pantoliano) and Natalie (Carrie-Anne Moss). The viewers of Memento find out pretty fast that a mentally ill character like the one of Leonard Shelby is an extremely unreliable narrator. Nollan gives us hints about the unreliability of human memory . [pic][pic] We can also see Leonard being manipulated by others and making mistakes while collecting information on his wife’s murderer. [pic][pic] We can see here that he mistakes the I of the license plate for a 1What is very interesting in the revenge story In addition to Leonard’s revenge story is the embedded story of Sammy Jankis and his wife which we will encounter in the sequence I have chosen to analyze. [pic] EXTRACT ANALYSIS Introduction The selected movie extract (1. 22. 58 – 1. 48. 43) is a sequence shot in Scope like the entire film is and in black and white as half of the movie’s sequences are. Those sequences were shot that way in order to be separated from the colored ones. Black and white sequences are shown in a chronologically forward order whilst the colored ones are shown backwards and don’t have a linear narrative structure.In this specific extract, Leonard Shelby narrates part of Sammy Jankis’s story, probably the most important one because it describes how he killed his wife by giving her an overdose of insulin. As it is explained to the viewers earlier in the film, Sammy suffers of the same condition as Leonard. Leonard investigated his case when he was still healthy and working for the insurance company and refused Sammy’s insurance claim by proving it was a psychological condition rather than a physical one. Relation between Stam’s text and the Memento sequenceStam refers in his chapter Narrators in Film and Novel to the case of â€Å"embedded narration† and how embedded narratives generate hypodiegesis. Hypodiegesis occurs when a substory is embedded within stories. In the case of this extract, the story is the one of Leonard’s hunting down his wife’s killer while dealing with his condition , and the substory , the one of Sammy Jankis’s condition and how his wife tries to deal with it. In the sequence Leonard is speaking on the phone with someone yet unknown to the viewers who is supposed to be a police officer.During their conversation, â€Å"Lenny† talks about his condition while comparing it to Sammyâ €™s and decides to speak about what happened to him and his wife. This is when hypodiegesis occurs. [pic] Once this embedded narrative begins we are the scene is no longer situated in the same place and the characters have changed. As Leonard narrates the camera serves as a visual manifestation of what he is describing. We see him in a room with Sammy’s wife crying just after we hear him speaking about how she came to see him in his office.Then he talks about how, persuaded he could â€Å"snap out of† this mental condition, she put him through his final exam. [pic][pic] Then we are transported back to the Jankis’s home where Leonard does not describe the fact that she tricks her husband into giving her three consecutive insulin shots (as it is shown) but only talks about how she found a way to test him hoping she would call his bluff. As Stam says â€Å"a voice over narration gradually gives way to direct monstration, yet we somehow take what is monstrated to emanate from the initial narrative†.What makes this substory so interesting is the fact that the story of Sammy Jankis may in fact be the story of Leonard Shelby. Perhaps this whole parallel story wants to show the viewer that Leonard's own wife was killed not by a murderer but by Leonard himself. There are several hints that point out the lack of the character’s reliability and lead us to conclude that his substory is a fabrication of his own subconscious. Reliability is actually a very interesting issue for Stam and in this case our narrator belongs to â€Å"those who are almost completely suspect† as they are called in Stam’s text.There are three important moments in the sequence that help us understand Leonard’s unreliability. The first one is when he takes in his hands a picture of himself (which later we learn it was took the moment he killed his wife’s murderer) and turns it the other way so that he doesn’t see it anymore. At the same time he says â€Å"It’s completely fucked because nobody believes you, it’s amazing what a little brain damage will do for your credibility. I guess it’s some kind of poetic justice for not believing Sammy†. [pic][pic] The fact that he hides the picture shows the viewers that he does not want to see it.He does not want to see himself while he tells Sammy‘s story, because he wants to forget that it is actually his story. He is lying to himself and wants to believe his lies. His words have also great meaning. He says that nobody believes him and that he has no credibility. He is again talking about himself because it is he that does not believe himself and he knows that he is not credible. His subconscious is projected to the viewers, we can see how deep inside he knows he is lying and he is fighting to believe these lies.As he says he didn’t believe Sammy, or, maybe he didn’t believe himself? The second hint is given to the sp ectators when he looks at one of his tattoos which is â€Å"remember Sammy Jankis† and at the same time says on the phone â€Å"Like Sammy. What if I‘d done something like Sammy? †. [pic] In this case, a doubt is raised, both in our minds and in Leonard’s mind. What if he had done something like Sammy? What if he had killed his wife without knowing it? The ending will show that he actually did kill his wife exactly how Sammy is supposed to have.The tattoo reminds him of Sammy, he needs that tattoo, he needs to be reminded of Sammy, otherwise there would be no meaning for him to continue on leaving. He needs to mask the facts in such a way so that he’ll have a purpose to go on. Remembering Sammy Jankis means to forget about what he did. The last moment that points out to Leonard’s lack of reliability is the most visual one. While Leonard describes how Sammy was put in a home after the death of his wife, we can see Sammy sitting in a chair at t he exact home. The camera starts to zoom in on him, when, at a certain point, a doctor passes in front of him and we have a cut.When the action starts again, the doctor gets out of the way and we can get a glimpse (for exactly 2 frames) of Leonard sitting in that same chair instead of Sammy, just before the scene ends. It is obvious that Nolan wants the viewers to see that Sammy and Leonard are the same person and that Leonard is actually describing his own story. [pic][pic] Conclusion Memento is a film with unique narrative structure. The story behind it is rather simple but the narrative structure is extremely elaborate and constant attention from its spectators is needed.The lack of short memory of the protagonist and and the chaos following him and his attempts to put together the puzzle of his wife’s murder are linked to whole storytelling in a very intelligent way. The fact that the main plot’s narrative structure is backwards and that its conclusion is revealed in the opening sequence, along with the mix of color and black and white sequences, can sometimes confuse the spectators as much as the main character. The spectators are this way driven to identify themselves in Leonard, sharing with him the confusion and the feelings of each revelation, as well as those of the disappointing truth.

Erik Eriksons Attachment Theory Essay - 836 Words

Erik H. Erikson was a significant psychologist that greatly changed the field of child development. In the 1950’s, Erikson advanced a Freudian approach in development. He viewed that social development as a series of eight challenges that people have to overcome. Each challenge has an outcome that’s either favorable or unfavorable. The outcome drastically affects a person’s personality. For example, in a favorable outcome, the result can leave a positive feeling. With a positive outlook, it’s easier for a person to cope with challenges in life. An unfavorable outcome can leave a person at a disadvantaged for the future. During the first couple challenges, Erikson believed that the caregiver has a great impact on a child’s development†¦show more content†¦If the toddler is able to explore with certain boundaries, the toddler will most likely develop a sense of self-sufficiency. On the other hand, if the parents are never satisfied with the t oddler’s effort and are overprotective, the toddler may develop a lack of confidence and shame (Romero). By definition, â€Å"attachment is the emotional bond between an infant and the primary caregiver (Romero; Perry).† During the first eight months of life, an infant will typically form an emotional attachment to a caregiver. The kind of attachment is based on the nurture and care the infant receives. The type of attachment between an infant and a caregiver can help determine the child’s personality and development (Romero). Secure attachment is commonly considered the healthiest style of attachment. This bond results when a caregiver responds to the child’s needs in an appropriate manner. The child will learn that the caregiver will be responsive and available (Romero). When parents provide a safe and secure environment, a child can build a nurturing relationship. Most of all, a child will simply feel valued and loved (Greenberg; Romero). In the future, a child with a secure attachment is empathetic and eager to try new things in life (Perry; Romero). A typical child has an optimistic attitude and they enjoy interacting with other people (Perry). Also, â€Å"Kids who were secure as infantsShow MoreRelatedTrust vs Mistrust Essay1271 Words   |  6 Pagesparents to ensure their infant’s needs are being met. In 1965 Erik Erikson developed eight psychosocial growth stages beginning with Stage 1, ‘trust vs. mistrust’, which occurs from birth and throughout the first year of an infant’s life (Candlin 2008, p.76). Erikson’s theory of ‘trust vs. mistrust’ will be outlined in this paper to suggest how it can be implemented to support parents in developing positive relationships and attachment with their infant and lay the foundations for trusting relationshipsRead MoreThe Theory Of Development Concepts And Applications By William Crain1076 Words   |  5 Pagesso many beautiful observations.   Our text Theories of Development Concepts and Applications by William Crain  outlines human development by many theorists.   A few of those are  John Bowlby,  Mary D.S. Ainsworth,  and  Ã‚  Erik H. Erikson.   I couldn t help but reminisce about the stages of my own children’s  growth while reading the work of Bowlby, Ainsworth and Erikson.   I remember having my  young children with me when ever it was possible, but what attachments to them might I have  missed while I  was busyRead MoreErik Erikson s Theory And Theory908 Words   |  4 PagesBoth Eri k Erikson’s theory and Mary Ainsworth and John Bowlby theory support the idea that early life experiences impact the person across their lifespan. Erikson’s developmental theory discusses the eight stages of life and the forces and values that arise at each stage, which should be developed within this frame. The attachment theory focuses on the interaction an individual has and the impact it may have on their psychological and social development. Both theories believe that personality beginsRead MoreDevelopmental Psychologist Erik Erikson s Stages Of Psychosocial Development1729 Words   |  7 PagesDevelopmental psychologist Erik Erikson changed the way that people viewed the psychosocial development in humans throughout their lifespan. Using the foundation provided by Freud’s psychosexual stages, he modified the concepts to where they demonstrated external impacts on development as well as making it more about emotional conflicts than necessarily physical dr ives. This eight-stage theory is sequential, and requires the person to overcome conflicts in each stage to become a productive memberRead MoreErik Eriksons Eight Developmental Stages Essay641 Words   |  3 PagesERIK ERIKSON’S EIGHT DEVELOPMENTAL STAGES Erik Erikson was a psychological pioneer well thought out before his time. Instead of dealing in psychosexual stages, he was discussing work in terms of psychosocial stages. Heavily influence by Freud and believing that personality played a huge part in the conflict within the ego itself, Erikson was the first ego psychologist. Believing that growth can take place well into adulthood, Erikson divided his eight stages into three that were going on simultaneouslyRead MoreApplication Of The Personality Theories Developed By Erik Erikson And Raymond Cattell1724 Words   |  7 PagesApplication of the Personality Theories Developed by Erik Erikson and Raymond Cattell â€Å"Personality is made up of the characteristic patterns of thoughts, feelings, and behaviors that make a person unique. It arises from within the individual and remains fairly consistent throughout life† (Cherry, 2014). My personality is influenced from my specific circumstances, my upbringing, and it is represented best through the theorists of Erik Erikson and Raymond Cattell. In specific circumstances my behaviorRead MoreIntroduction. Erik Erickson’S Interest In How One’S Environment1646 Words   |  7 Pages Introduction Erik Erickson’s interest in how one’s environment and social interaction drives human behavior and the development of personality, led him to create the psychosocial theory, â€Å"Eight Stages of Man.† Erikson’s final four stages of psychosocial development describes a person’s development from adolescence to late adulthood. This paper will analyze the final four stages of development, which includes: Adolescence, Young Adulthood, Middle Adulthood, and Late Adulthood. However, one of theRead MoreWhat is Psychosocial Development?948 Words   |  4 PagesA man named Erik Erikson who was a psychoanalyst who believed that early childhood successes and failures were responsible for influencing later developmental stages developed this theory. Erikson’s theory of psychosocial development is based around the theory that social experience has an impact over an entire lifespan. There are eight stages developmental stages of development in the psycho social theory and I will briefly examine all eight stages in this paper. Erik Erikson is bestRead MoreThe Theory Of Cognitive Development1127 Words   |  5 PagesPiaget, Erik Erikson, and John Bowlby have theorized what happens in this stage of life. Theorists Piaget came up with the Theory of cognitive development. The theory of cognitive development has four stages. Sensorimotor is the first stage. The first stage of Piaget s theory lasts from birth to approximately about the age of two. This stage is centered on the infant trying to make sense of the world around them through hearing, seeing, smelling, touching, tasting, and feeling. Erik Erikson developedRead MoreEcological Systems Theory By Urie Bronfenbrenner1556 Words   |  7 PagesEcological Systems Theory The Ecological Systems Theory was founded by Urie Bronfenbrenner. This theory focuses on the impact of the environment on a child’s overall development. The identifying characteristics of Bronfenbrenner’s theory are the five systems used to organize external influences within a child’s development. These systems are the microsystem, mesosystem, exosystem, macrosystem, and chronosystem. Each system is aligned with specific interaction levels. The microsystem is considered