Ultrawide-bandwidth, superluminescent light-emitting diodes using InAs quantum dots of tuned height.

An ultrawide-bandwidth, superluminescent light-emitting diode (SLED) utilizing multiple layers of dots of tuned height is reported. Due to thermal effect, the superluminescent phenomenon is observed only under pulse-mode operation. The device exhibits a 3 dB bandwidth of 190 nm with central wavelength of 1020 nm under continuous-wave (cw) conditions. The maximum corresponding output power achieved in this device under cw and pulsed operation conditions are 0.54 mW and 17 mW, respectively.

All-optical, fiber-optic modulator and logic gate using nonlinear refraction and absorption.

The first demonstration to our knowledge of new all-optical logic gates and modulators that use nonlinear refraction and absorption to modify fiber-to-fiber coupling is reported. Results are presented for the AND, NOR, NOT, and XOR functions with better than 20-dB contrast ratio. Silicon (at lambda = 1.06 microm) is used as the nonlinear material for this proof-of-concept experiment. No resonators, feedback, or stringent wavelength controls are needed. The feasibility of picosecond operation is discussed.

Nanosecond-laser-induced optical wave mixing and ultrasonic wave generation in the nematic phase of liquid crystals.

We have quantitatively observed for the first reported time nanosecond-laser-induced optical wave mixing and ultrasonic wave generation in nematic liquid-crystal films. The effect may prove useful for microsecond wave-front conjugation with a moderate-power laser or gigahertz acousto-optic switching.

Quasi-phase-matched second-harmonic generation from asymmetric coupled quantum wells.

Optical second-harmonic generation of visible light in a superlattice of asymmetric coupled GaAs quantum wells has been measured for the first time to our knowledge. The orientation of the asymmetric quantum wells was periodically reversed such that the quantum-well contribution to the radiated second-harmonic signal was quasi-phase matched when it was excited by a lambda = 1.319 microm fundamental in the reflection geometry. The second-harmonic intensity generated in this superlattice was approximately 3.6 times that generated in a homogeneous GaAs reference. The measured superlattice second-harmonic susceptibilities are[Equation] and[Equetion].

Coherent phase and frequency detection by using sum-frequency mixing in nonlinear waveguides.

We demonstrate a novel optical phase detector that uses sum-frequency mixing in a nonlinear waveguide. By monitoring the near-field pattern of the sum-frequency light radiated from the waveguide surface, the relative phase of two input light beams can be measured. By using an Al(x)Ga(1-x)As waveguide optimized for sum-frequency generation with lambda = 1.06 microm input light, we demonstrate a simple phase detector capable of resolving phase shifts of less than 0.2 rad. This phase detector is also used in an interferometer configuration as a gigahertz-resolution frequency monitor.

Electrooptic-photorefractive modulation in Ti:LiNbO(3) waveguides.

A simple inexpensive modulator based on a combination of the photorefractive and electrooptic effects in Ti:in-diffused LiNbO(3) waveguides is demonstrated.

High-resolution surface-emitting spectrometer and deformation sensors with nonlinear waveguides.

We investigate the limits of frequency resolution attainable in a nonlinear waveguide optical spectrometer, including the effects that are due to surface distortions and waveguide inhomogeneities, and demonstrate that the frequency-resolving capability is directly scalable with the radiating aperture length. The resolution of the waveguide is diffraction limited, and therefore the far-field radiation pattern can be used to characterize the phase variations along the waveguide that are due to surface distortions. The use of this device as a highly sensitive deformation sensor is demonstrated by application of a distortion to the waveguide and confirmation of the far-field diffraction pattern generated.