Search

We have analyzed the transmitted spectra of optical elements including the phase gratings and Fabry-Perot (FP) and found design parameters of these elements for the elimination/reduction of on-axis transmission of broadband of visible light. In this paper, we will present a detailed theoretical analysis on the design and performance of the optical elements that will greatly reduce the transmittance of the beam in its original path of propagation. We will give the numerical computation results derived from the formula showing the spectral dependence of the direct intensity transmittance for different optical elements.

Progress in optical computing, optical communication and optical information processing depends on a large extent of the availability of fast all-optical switches. Most of the all-optical switches utilize nonlinear FP cavity1,2,3. Its absorptive loss is very large because of working on the resonant wavelength, and the switching time is districted by the response time of cavity. In 1990 K. W. Beeson4 presented a novel all-optical switch based on the triplet-triplet absorption in Eosin Y using a CW laser as a pump beam, and obtained μs scale switching time. We developed this kind of switches in C605 whose switch off time was about 250 ns which depends on the lifetime of the first triplet excited state.

Photosensitive organic materials are showing promise as versatile candidates in the filed of information storage due to their special advantages: low cost, easy to handle, real-time recording capabilities, fast response time, wide frequency band and large third-order nonlinear susceptibility. The experiments were mainly focused on the resonant absorption region of materials because the resonant light may enhance the third-order nonlinear susceptibility and storage capability. In this paper, we report the experimental results of nonresonant real-time holographic memories on a azo-dye doped polymer (ADP) film. The ADP film shows quite large nonresonant third-order nonlinearity and real-time polarization holographic memories properties.

Recently, studies on the photophysical properties of C60 have shown that the population of the first excited singlet state(S1) can be transferred to the first excited triplet state (T1) with a quantum yield higher than 96% by intersystem crossing with a relaxation time about 1ns.

Optical limiting in toluene solution of C60 is first observed by L. W. Tutt and A. Kost,1 which is caused from reverse saturable absorption (RSA) of C60.

In the past decade, experimental results of transient optical bistabilities in etalons of CdSxSe1-x doped glasses have been presented by many authors[1-3]. Switching speed of ns to ps orders has been obtained. However, there still do not exist a dynamics theory of this transient optical bistability. This paper emphasizes the dependence of the implementation of transient optical bistabilities on the incident pulse width, the media response time, the FP cavity establishing time, and also, the influence of the incident pulse width on the switching speed.

Saturable absorption (SA) in organometallic compounds, such as phthalocyanine (Pc), was extensively studied in 1960’s, the purpose of the research was to find suitable dyes to compress laser pulse. As we know, SA is due to the absorption of the ground state, which can be described by a two-level model or a three-level model[1]. At that time, the excited state absorption, only considered as residual absorption, had not received much attention.

The excitonic optical nonlinearities in II-VI semiconductor thin films and multiple quantum wells (MQWs) are much complicated than those of GaAs MQWs because the wider band gap and smaller excitons of II-VI semiconductor materials. We report here the observations of dynamic optical bistabilities in ZnSe/ZnS MQWs at low temperature caused by excitonic optical nonlinearity.

Multiple-valued logic offers many times the logic power and packing desity of binary logic, thus reducing the number of necessary logic gates.1 Recently optical multip1e-va1ued logic has been studied extensively using shadow casting method.2 In this paper we describe a new configuration of optical multiple-valued logic gates using composite bistable laser diode or light emitting diode circuits (BILD or BILED). To our knowledge, this is the first time that optical multip1e-va1ued logic have been obtained using optical bistable device. We have demonstrated four Post logic functions: Complement, Max(x,y), Min(x.y), and Suc(x) using composite BILED circuits. We only take Complement and Max(x,y) for example here.

Integrated optoelectronic logic circuits are promising for use in optical computing. Much attention has been paid to demonstrate binary and multiple-valued optical logic implementation using optoelectronic circuits. In this paper we present what we believe to be the first demonstration of optical binary threshold logic using a modified optoelectronic PD LED bistable circuit (BILED).

Relaxation oscillation can occur in a bistable system when the nonlinearity has two contributions of opposite sign and different time constants.1 Optoelectronic bistable laser diode or light emitting diode (BILD or BILED) circuit is a promising optical logic device.2 Here we present the observation and analysis of optical regenerative pulsation in a system constructed of a liquid crystal switch and BILED circuit. Sine wavelike pulses were obtained in our experiment, and the experimental results show that the oscillation frequencies were stable. The frequency can be adjusted by changing the voltage supply. In our experiment the output from an argon laser is controlled by a LC switch, which is connected to a BILED circuit. The voltage applied across the LC switch is provided by an amplifier, and it is proportional to the output of the BILED circuit. The BILED circuit has two output signals of feedback. One is the light emitted from the LED in the circuit. The other is a part of the laser beam transmitted from the LC switch. As oscillation occurs in the circuit, the laser beam is modulated into a train of pulses by the LC switch.