© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Topical Meeting on Optical Bistability (OB)

Low Power Optical Bistability Near Bound Excitons in Cadmium Sulfide

M. Dagenais, H. G. Winful

Published Jan 1, 1983• 0 citations

Abstract

The I2 bound exciton in cadmium sulfide has a giant oscillator strength of 6. It decays mostly radiatively in 500 psec. Such a large oscillator strength leads to a very large transition dipole moment and to very large nonlinear effects off-resonance. At 2K, this sytem saturates like an inhomogeneously broadened system for intensities up to 30 times the saturation intensity. The transition linewidth is 7.5 GHz. In a tight focusing geometry, only 3.6 μW is required to see the onset of saturation. This corresponds to a measured saturation intensity of about 60 W/cm2. The linear absorption coefficient right at the resonance peak was measured to be 3.2 x 103 cm-1. At higher temperatures, the transition linewidth broadens and the line becomes more and more homogeneously broadened because of phonon interaction. At intensities above 50 times the saturation intensity, the absorption coefficient stops decreasing and then starts increasing. At these high intensities, thermal effects appear to play a significant role in shifting the free and bound exciton resonances toward lower energies. At intensities less than 20 times the saturation intensity, thermal effects are believed to be insignificant in our saturation measurements.

DOI: 10.1364/obi.1983.fb2

Related papers

Low power optical saturation of bound excitons with giant oscillator strength

M. Dagenais

The optical saturation of the I2 bound exciton in cadmium sulfide, an exciton bound to a donor, is reported. This system, which decays radiatively in 500 ps, can be saturated with a cw power of only 3.6 μW, which is equivalent to a saturation intensity of 58 W/cm2. Good agreement is found with the predictions of an inhomogeneously broadened two-level system. Thermal effects appear to play a minimal role.

Applied Physics Letters•Oct 15, 1983•28 citations

Low-power saturation of bound excitons and observation of optical bistability

M. Dagenais, Herbert G. Winful

Very large nonlinearities are observed in the vicinity of a bound exciton resonance in cadmium sulfide. Power levels of the order of 8 μW are sufficient for saturating the bound exciton resonance in a tight focusing geometry. In a more loosely focused geometry, power levels of the order of 250 μW are sufficient for saturating the bound exciton resonance and for observing optical bistability. Transverse effects are found to play a very important role. For all our measurements, no thermal contributions to the nonlinearity were observed. Since thermal effects are not playing a role and since the studied bound excitons decay radiatively in 500 psec, we infer subnanosecond switchoff and cycling times.

Conference on Lasers and Electro-Optics•Jan 1, 1983•1 citation

Cavityless optical bistability due to light-induced absorption in cadmium sulfide

M. Dagenais, Wayne F. Sharfin

Cavityless, whole-beam optical bistability in thin, uncoated cadmium sulfide platelets is observed at milliwatt power levels when a cw laser is tuned near a sharp extrinsic excitonic resonance in cadmium sulfide (the I2 bound exciton). Very large contrast ratios between the on and off states are measured. The detuning and temperature dependence of the bistability results are reported. Preliminary transient measurements are also discussed.

Applied Physics Letters•Aug 1, 1984•70 citations

Internal Feedback Mechanisms of Optoelectronic Bistability in Cadmium Sulfide

Sergey Viktorovich Bogdanov, Vadim G. Lyssenko

Optical bistability caused by thermal heating is observed when the CdS crystal is excited near the I2 bound exciton absorption line [1]. Impact ionization of free and bound excitons occurs in the crystal upon its illumination in electric field. The probability of impact ionization depends in a threshold way on exciton and free carrier concentration. At a certain field dependent carrier concentratiοn avalanche occurs, the electric current therewith increases the crystal temperature by 5-20 K [2] which is followed by a red I2 shift. The shift leads to an increase in absorption, carrier density and current. Therefore, feedback results from impact ionization current heating the crystal (Fig. 1).

Topical Meeting on Optical Bistability (OB)•Jan 1, 1988•0 citations

Picojoule, subnanosecond, all-optical switching using bound excitons in CdS

M. Dagenais, Wayne F. Sharfin

We use the nondiffusive nonlinearity, the large transition dipole moment, and the small spectral broadening associated with the I2 bound excitons in cadmium sulfide to achieve the lowest reported single beam switching energy (<8 pJ) and the fastest reported ON/OFF switching bistable device (<2 ns) with clearly resolved switching states. In an optimized geometry, it is shown that the fundamental limits on switching energies can be approached.

Applied Physics Letters•Feb 1, 1985•52 citations

Low power transverse optical bistability near bound excitons in cadmium sulfide

M. Dagenais, Herbert G. Winful

We report the observation of cw transverse optical bistability without power hysteresis at 1-mW power levels in uncoated cadmium sulfide platelets. Optically induced refractive index changes as large as 0.15 are deduced from measurements of the transverse spatial ring profile.

Applied Physics Letters•Mar 15, 1984•33 citations

The I2 bound exciton in cadmium sulfide has a giant oscillator strength of 6. It decays mostly radiatively in 500 psec. Such a large oscillator strength leads to a very large transition dipole moment and to very large nonlinear effects off-resonance. At 2K, this sytem saturates like an inhomogeneously broadened system for intensities up to 30 times the saturation intensity. The transition linewidth is 7.5 GHz. In a tight focusing geometry, only 3.6 μW is required to see the onset of saturation. This corresponds to a measured saturation intensity of about 60 W/cm2. The linear absorption coefficient right at the resonance peak was measured to be 3.2 x 103 cm-1. At higher temperatures, the transition linewidth broadens and the line becomes more and more homogeneously broadened because of phonon interaction. At intensities above 50 times the saturation intensity, the absorption coefficient stops decreasing and then starts increasing. At these high intensities, thermal effects appear to play a significant role in shifting the free and bound exciton resonances toward lower energies. At intensities less than 20 times the saturation intensity, thermal effects are believed to be insignificant in our saturation measurements.

Very large nonlinearities are observed in the vicinity of a bound exciton resonance in cadmium sulfide. Power levels of the order of 8 μW are sufficient for saturating the bound exciton resonance in a tight focusing geometry. In a more loosely focused geometry, power levels of the order of 250 μW are sufficient for saturating the bound exciton resonance and for observing optical bistability. Transverse effects are found to play a very important role. For all our measurements, no thermal contributions to the nonlinearity were observed. Since thermal effects are not playing a role and since the studied bound excitons decay radiatively in 500 psec, we infer subnanosecond switchoff and cycling times.

Optical bistability caused by thermal heating is observed when the CdS crystal is excited near the I2 bound exciton absorption line [1]. Impact ionization of free and bound excitons occurs in the crystal upon its illumination in electric field. The probability of impact ionization depends in a threshold way on exciton and free carrier concentration. At a certain field dependent carrier concentratiοn avalanche occurs, the electric current therewith increases the crystal temperature by 5-20 K [2] which is followed by a red I2 shift. The shift leads to an increase in absorption, carrier density and current. Therefore, feedback results from impact ionization current heating the crystal (Fig. 1).