G.T. Kennedy

Spin relaxation and all optical polarization switching at 1.52 micrometres in InGaAs(P)/InGaAsP multiple quantum wells

The spin relaxation times of electrons in InGaAs(P)/InGaAsP multiple quantum wells have been directly measured as a function of well width using an ultrashort pulse colour centre laser. The times measured range from 20 to 5 ps, considerably faster than previously determined in GaAs quantum wells. In addition, a fast, all-optical polarization switch based on a spin-sensitive optical nonlinearity is demonstrated at a wavelength of . This operating wavelength and the observed switch recovery time of 5.5 ps make it a potentially useful element for future all-optical soliton communication systems.

Widely tunable, near- to mid-infrared femtosecond and picosecond optical parametric oscillators using periodically poled LiNbO/sub 3/ and RbTiOAsO/sub 4/

We describe the operation and characterization of Ti:sapphire laser-pumped femtosecond and picosecond optical parametric oscillators based the new quasi-phase-matched nonlinear materials of periodically poled LiNbO/sub 3/ and RbTiOAsO/sub 4/ with broad tunability in the near- to mid-infrared. We discuss the merits of the two materials for use in ultrafast optical parametric oscillators (OPOs) and compare and contrast their properties to the birefringent materials. We demonstrate an extended spectral coverage from 5 /spl mu/m, pump power thresholds as low as 45 mW, average mid-infrared output powers in excess of 100 mW, and pulse durations of 100-200 fs and 1-2 ps at /spl sim/80 MHz repetition rate. We also report the efficient operation of Ti:sapphire-pumped femtosecond OPOs in all-solid-state configurations by utilizing diode-laser-based input pump sources.

Near- to mid-infrared picosecond optical parametric oscillator based on periodically poled RbTiOAsO(4).

We describe a Ti:sapphire-pumped picosecond optical parametric oscillator based on periodically poled RbTiOAsO(4) that is broadly tunable in the near to mid infrared. A 4.5-mm single-grating crystal at room temperature in combination with pump wavelength tuning provided access to a continuous-tuning range from 3.35 to 5microm , and a pump power threshold of 90 mW was measured. Average mid-infrared output powers in excess of 100 mW and total output powers of 400 mW in ~1-ps pulses were obtained at 33% extraction efficiency.

All-optical polarisation switching at 1.5 /spl mu/m in In/sub 1-x/Ga/sub x/As/sub y/(P/sub 1-y/)-InGaAsP multiple quantum wells

Summary form only given. All-optical polarisation switches based on the excitation of spin polarised electrons in GaAs multiple quantum wells (MQWs) have been demonstrated previously with recovery times in the range 20 to 80 ps at wavelengths around 850 nm. In this work, we have studied the well width dependence of spin-dependent optical nonlinearities and spin relaxation times in InGaAsP MQWs and demonstrated all-optical polarisation switching with a recovery time as short as 5.5 ps at wavelengths compatible with all-optical soliton communication systems.

Mid-infrared picosecond optical parametric oscillator based on periodically poled RbTiOAsO/sub 4/

Summary form only given. The advent of quasi-phase-matched (QPM) nonlinear materials such as periodically poled LiNbO/sub 3/ (PPLN) has provided valuable additions to the existing birefringent materials for use in ultrafast OPOs. In particular, the potential of PPLN for use in a Ti:sapphire-pumped picosecond OPO for the 1- to 2.5-/spl mu/m region was recently demonstrated. We have now extended the operation of these devices into the mid-infrared by exploiting the new QPM nonlinear material periodically poled RbTiOAsO/sub 4/.

Exciton Absorption Saturation and Carrier Transport in Quantum Well Semiconductors

Optical nonlinearities [1–4] associated with excitonic absorption features in multiple quantum well (MQW) semiconductors [5] offer a number of useful functions for optoelectronics devices [6,7]. These include laser mode-locking elements, saturable elements for controlling the propagation of optical solitons in fibre transmission systems, all-optical bistable etalons, all-optical directional coupler switches and self-electro-optic devices for communications, signal processing and computing. The operation and optimisation of these devices rely on an understanding of the mechanisms which contribute to absorption saturation and the motion of optically generated electrons and holes in directions both parallel and perpendicular to the quantum wells. This chapter reviews measurements of exciton absorption saturation mechanisms and in-well transport processes relevant to new optoelectronic electro-optic and nonlinear optical devices.