In this paper we report for the first time the presence of bistability in an acoustic-optic tunable filter (AOTF) operating with ultrashort (2 ps) optical light pulses. The results for the study of bistability has shown the dependence of the hysteresis curve with the product of the coupling constant (κ) by the length of the device (ξL) and the conversion power-coupling constant factor (G). The range of bistability varies significantly with both G and with κξL parameters. The variation of κξL directly increases the size of the range of bistability hysteresis while the increase in G causes the bistability to occur at low powers. The phenomenon of optical bistability (OB) is the object of increasing interest due to its possibilities for important device applications. A bistable device is a device with a capability to generate two different outputs for a given input and the physical requirements for this are an intensity-dependence refractive index and an optical feedback mechanism.
In this paper we report for the first time the presence of bistability in an acoustic-optic tunable filter (AOTF) operating with ultrashort (2 ps) optical light pulses. The results for the study of bistability has shown the dependence of the hysteresis curve with the product of the coupling constant (κ) by the length of the device (ξL) and the conversion power-coupling constant factor (G). The range of bistability varies significantly with both G and with κξL parameters. The variation of κξL directly increases the size of the range of bistability hysteresis while the increase in G causes the bistability to occur at low powers. The phenomenon of optical bistability (OB) is the object of increasing interest due to its possibilities for important device applications. A bistable device is a device with a capability to generate two different outputs for a given input and the physical requirements for this are an intensity-dependence refractive index and an optical feedback mechanism.
Optical bistability (OB) can be defined as the existence of two stable states for one set of optical input conditions. It can be seen in many different systems which generally combine some microscopic nonlinearity (e.g., intensity-dependent refractive index) with some macroscopic feedback (e.g., a Fabry-Perot cavity). OB shows not only hysteresis but also switching transitions. By adjusting the degree of feedback various related effects are also possible (e.g., optical limiters, optical transistors, and several kinds of oscillation phenomena).
When the output parameter of an optical device could be a multivalued function of the input parameter, this device can be working in an optical bistable status. The most typical optical bistable device is a Fabry–Perot cavity containing a nonlinear optical medium, the refractive index of which depends on the light intensity. Upon the action of an intense input optical beam, the transmitted (or reflected) intensity of this device may exhibit a nonlinear response to the incident light intensity variation and, especially under appropriate working conditions, the characteristic output/input curve may manifest a single (or multiple) hysteresis loop(s). Such type of optical bistable device can be used as an optical differential amplifier, optical switch, optical limiter, optical clipper, optical discriminator, or an optical memory element, depending on the chosen nonlinear medium and operation conditions.
Previous research with acousto-optic hybrid optical/electronic (HOE) bistable devices has been directed towards operation in the first Bragg regime.1 We have demonstrated several simulations and experiments to study a HOE bistable system in the second Bragg regime. In this bistable system, the acousto-optic device operates in the second order with the light incident at twice the Bragg angle. To achieve optical bistability, the second order diffracted light is detected by a photodetector, amplified with a linear amplifier, summed with a bias voltage, and feedback to the acousto-optic device. The operation of the acousto-optic device can be explained by a set of coupled differential equations. Likewise, the feedback loop can be modeled with a feedback equation. The simultaneous solution of these equations provided our theoretical model. In this talk, we will compare theoretical and experimental results, as well as compare first order and second order operation.
In this work, we studied the optical bistability of Fiber Bragg Grating (FBG) under nonlinear regime, considering three increasing and decreasing profiles of nonlinearity: linear, quadratic and exponential. We varied the nonlinearity range in each profile, and obtained different curves of bistability and reflectivity. We analyzed the powers [Formula: see text] and [Formula: see text], as well as the width of the photonic band gap ([Formula: see text] of each device under different nonlinearity profiles, and we observed the changes in reflectivity of the FBG. The power intensities [Formula: see text] and [Formula: see text] obtained for the bistability of decreasing profiles were lower than those obtained for the increasing profiles, and the values of [Formula: see text] were also lower in decreasing profiles, which is useful for optical switching applications.
From the frequency dependence of the optical transmission characteristics of Raman-Nath acoustic-optic diffraction, the dynamic equations and steady-state solutions of a two-dimensional Raman-Nath acousto-optic bistable system are derived. In this system, feedback is realized by use of a diffracted light beam to control the frequency of the acoustic-optic driver. The curves of light output versus input corresponding to several orders of the diffracted beams are obtained by theoretical analysis. They can all lead to bistability. The amount of hysteresis is a function of the order of the diffracted beam, the bias frequency, and the feedback coefficient. Experimental results are presented and compared with theoretical analyses.
Traditional frequency domain optical bistability(FDOB) devices with hybrid electro-optical feedback have low response speed and high noise fluctuations.Hence,a novel tunable laser FDOB device with an all-optical feedback was developed using a nonlinear fiber ring resonator as the frequency feedback element.Parametric equations of optical bistability were established according to the system's response to nonlinear process and frequency-dependent feedback.Based on the parametric equations,the characteristics and controllable operations of FDOB were analyzed.The switching response speed of the optical bistability was discussed.The analysis showed that the proposed all-fiber laser bistability device can effectively achieve intensity-driven and gain-driven optical bistability.The position and shape of the bistability hysteresis curve vary with the adjustment of gain or loss in the fiber ring resonator,hence realizing the controlled all-optical bistability operations.Sudden jumping of optical bistability in the frequency domain can be applied to monitor laser wavelength shift and achieve sensoring.The optical bistability response time is in the nanosecond order of magnitude and bistability switching is ultrafast.