Low-power Optical Bistability Research Articles

Low power optical bistability from quantum dots in a nanobeam photonic crystal cavity

We demonstrate a low power thermally induced optical bistability at telecom wavelengths and room temperature using a nanobeam photonic crystal cavity embedded with an ensemble of quantum dots. The nanobeam photonic crystal cavity is transfer-printed onto the edge of a carrier chip for thermal isolation of the cavity with an efficient optical coupling between the nanobeam waveguide and optical setup. Reflectivity measurements performed with a tunable laser reveal the thermo-optic nature of the nonlinearity. A bistability power threshold as low as 23 μW and an on/off response contrast of 6.02 dB are achieved from a cavity with a moderately low quality factor of 2830. Our device provides optical bistability at power levels an order of magnitude lower than previous quantum-dot-based devices.

Low-power optical bistability in PT-symmetric chirped Bragg gratings with four-wave mixing

The central theme of this paper is the analysis of the usefulness of introducing four-wave mixing or modulation of Kerr nonlinearity in a nonuniform grating structure with gain and loss. To do so, we propose an inhomogeneous system in which the nonlinearity of the parity-time ( P T )-symmetric grating is modulated. It is proven that the proposed scheme can be fruitful only if the nonlinearity and its associated modulation terms are assumed to be self-defocusing. To cut down the intensity required for steering, the sign of chirping is taken to be negative, and the wavelength of operating light is considered to be higher than the Bragg wavelength. Alongside these settings, launching the light from the rear end of the device dramatically reduces the critical intensity to a value of 0.015 (approximately), which must be the lowest switching intensity ever reported in the context of nonlinear P T -symmetric gratings, to our knowledge. The ramp-like stable states in the broken P T -symmetric regime prevail even in the company of modulation in the nonlinearity index for both light incident directions.

Low-power optical bistability and hysteresis in the laser system with absorbing nanosuspension.

We demonstrate an optical bistability in a laser system with incoherent optical feedback and a nanosuspension as a nonlinear element. The optical transfer function is shown to exhibit a hysteresis loop for the light power in the range of a few milliwatts. It has been found that the optical bistability relies on the incoherent optical feedback and thermal defocusing nonlinear optical response of the nanosuspension.

Low-power optical bistability in a free-standing silicon ring resonator

We demonstrate low-power thermo-optic-based optical bistability in a free-standing silicon ring resonator. A bistable optical response is achieved at reduced pump powers by thermally isolating the ring resonator from its supporting substrate with an air gap. The conversion efficiency from optical power to temperature change in the silicon core is enhanced. The optical transfer function of the resulting free-standing resonator exhibits a hysteresis loop for 80 microW input optical power. Similar nonthermally isolated resonators at the same detuning do not exhibit a bistable mode for input powers less than 2 mW.

Extremely low power optical bistability in silicon demonstrated using 1D photonic crystal nanocavity

We demonstrate optical bistability in silicon using a high-Q (Q > 105) one-dimensional photonic crystal nanocavity at an extremely low 1.6 microW input power that is one tenth the previously reported value. Owing to the device's unique geometrical structure, light and heat efficiently confine in a very small region, enabling strong thermo-optic confinement. We also showed with numerical analyses that this device can operate at a speed of approximately 0.5 micros.

All-optical bistable switching in curved microfiber-coupled photonic crystal resonators

The authors report low-power optical bistability under continuous wave pumping conditions in five-cell photonic crystal linear resonators containing InGaAsP quantum wells, by employing the fiber-coupling technique. The threshold bistable power is measured to be 35μW at the normalized detuning of −1.724. Owing to the high band-edge nonlinearities of quantum wells and the efficient fiber coupling, minimal instability is observed. In addition, all-optical switching is demonstrated with switching energy less than 75.4fJ.

Submilliwatt optical bistability in wafer fused vertical cavity at 1.55-μm wavelength

We report on low-power optical bistability in a vertical cavity structure at 1.55-/spl mu/m wavelength due to the bandgap resonant dispersive optical nonlinearity of InGaAsP. In this structure, a GaAs-AlAs Bragg reflector grown on GaAs and the nonlinear medium grown on InP are bonded through wafer-fusion, leading to a high-quality vertical cavity after deposition of a top dielectric mirror. This device shows interesting characteristics for optical switching applications at fiber communication wavelengths, such as a switching contrast higher than 8:1 in the reflective mode and a bistability threshold power as low as 0.6 mW. True steady-state memory effect is observed with continuous-wave input, and the device switching time is in the ns range.

All-optical bistable switching in an active InGaAs quantum-well waveguide

The authors have observed low-power optical bistability in an active strained InGaAs single-quantum-well waveguide which is biased with a quasi-constant current injection 20% below the threshold current. Although the output power measured after the output collecting lens is half of the peak input power measured before the input focusing lens, it is believed that this is mainly due to the inefficient coupling into a slab mode, and that optical switching occurs with net gain in the device. A channel waveguide with a similar active medium would operate with constant DC electrical bias and should provide significant overall gain. >

Low-power optical bistability in a thermally stable AlGaAs étalon

Optical bistability with 10 mW input power is reported in a thermally stable, nonlinear AlGaAs étalon. A 3-μm-thick silver layer, which serves both as high-reflecting mirror and heat sink, makes it possible to operate the device at arbitrary duty cycles and pulse lengths up to 0.5 s, without any regenerative pulsations, at room temperature. The device operation depends on the plasma-induced electronic nonlinearity, and switching times are typically 10 ns. Device performance is compared with results from a numerical model which takes diffraction, diffusion, and heat conduction into account.

Optical Bistable Devices for Memory and Logic

Nonlinear interference filters and liquid crystal cells for low power optical bistability are reviewed. The use of filters for prototype optical circuitry and a proposed cellular-logic-image-processing architecture are described

Low-power optical bistability and phase conjugation in polydiacetylene

Optical bistability is reported at 514 nm using a Fabry-Perot cavity filled with a polydiacetylene/toluene solution or a polydiacetylene/ polyvinylchloride film. Swithch-up powers of less than 4 mW are observed. The nature of the nonlinearity is a thermally induced refractive index change. Simultaneous degenerate four-wave mixing shows corresponding bistable behaviour of the phase conjugate signal.

Low-power optical bistability and multistability in a self-electro-optic silicon interferometer

A novel hybrid semiconductor device is presented which shows optical bistability and a clear optical multistability at milliwatt input powers. Experimentally, a silicon etalon is used as a Fabry-Perot interferometer where an electric field is additionally applied by using integrated electrical contacts. At 1.06 μm the device exhibits the combined properties of a photodetector and an optical modulator. Due to this self-electro-optic effect a large optical nonlinearity is achieved which is theoretically attributed to electrical and optical heating of the sample.

Giant nonlinearities and low power optical bistability in cadmium sulphide platelets

Both whole-beam and transverse continuous wave optical bistability are observed at milliwatt power levels near the band gap in thin uncoated cadmium sulphide platelets. The whole-beam bistability is free from cavities and requires an absorption coefficient that increases with intensity.

Use of a diode laser to observe room-temperature, low-power optical bistability in a GaAs-AlGaAs etalon

Optical bistability is observed using a single-mode diode laser in a GaAs-AlGaAs multiple-quantum-well etalon with as low as six mW power at 830 nm.