Steve Sanders

Laser diode pumped 106 mW blue upconversion fiber laser

A laser diode pumped Tm3+‐doped ZBLAN fiber upconversion laser is demonstrated with blue output power levels up to 106 mW. Differential optical‐to‐optical conversion efficiencies up to 30% are measured with respect to pump power coupled into the upconversion fiber. A single spatial mode blue output beam is demonstrated, with an M2 value of 1.4.

108 GHz passive mode locking of a multiple quantum well semiconductor laser with an intracavity absorber

A two‐section multiple quantum well laser is passively mode locked without an external cavity at ∼108 GHz. The pulse widths average 2.4 ps and have a time‐bandwidth product of 1.1. Self‐pulsations at frequencies up to 8 GHz are also observed.

Submilliampere threshold current pseudomorphic InGaAs/AlGaAs buried-heterostructure quantum well lasers grown by molecular beam epitaxy

We report on low threshold current strained InGaAs/AlGaAs single quantum well lasers grown by molecular beam epitaxy. Broad-area threshold current densities of 114 A/cm2 at 990 nm were measured for 1540-µm-long lasers. Threshold currents of 2.4 mA at 950 nm were obtained for an uncoated buried-heterostructure device with a 2-µm-wide stripe and 425-µm-long cavity. With reflective coatings the best device showed 0.9 mA threshold current (L=225 µm). Preliminary modulation measurements show bandwidths up to 5.5 GHz limited by the detector response.

Submilliamp threshold InGaAs-GaAs strained layer quantum-well laser

Strained-layer InGaAs-GaAs single-quantum-well buried-heterostructure lasers were fabricated by a hybrid beam epitaxy and liquid-phase epitaxy technique. Very low threshold currents, 2.4 mA for an uncoated laser (L=425 mu m) and 0.75 mA for a coated laser (R approximately 0.9, L=198 mu m), were obtained. A 3-dB modulation bandwidth of 7.6 GHz was demonstrated at low bias current (14 mA). Procedures for material preparation and device fabrication are introduced. >

Passive mode locking of a two‐section multiple quantum well laser at harmonics of the cavity round‐trip frequency

A multiple quantum well GaAs/AlGaAs laser with two electrically isolated contacts is passively mode locked in an external cavity at the first through sixth harmonics of the pulse round‐trip frequency of 1.17 GHz to produce pulses shorter than 10 ps. The repetition rate is switched between harmonics by adjusting the gain section current, and large hysteresis between the different repetition rates is observed, with up to four different repetition rates for the same gain current. The results are compared with small and large signal passive mode‐locking theories by considering modifications to the saturated gain recovery between pulses when the laser operates at different harmonics.

Effect of Al mole fraction on carrier diffusion lengths and lifetimes in AlxGa1−xAs

The ambipolar diffusion length and carrier lifetime are measured in AlxGa1−xAs for several mole fractions in the interval 0<x<0.38. These parameters are found to have significantly higher values in the higher mole fraction samples. These increases are attributed to occupation of states in the indirect valleys, and supporting calculations are presented.

110 W fiber laser

We demonstrate a Yb-doped double-clad fiber laser with record average power output of >110 W cw in a single spatial mode beam. The conversion efficiency was /spl sim/58% with respect to the incident pump power.

Reduction of the intensity noise from an erbium-doped fiber laser to the standard quantum limit by intracavity spectral filtering

The high frequency intensity noise of a tandem fiber Fabry–Perot erbium-doped fiber ring laser is reduced to the standard quantum limit, with a 0.5 dB experimental uncertainty. Noise reduction of >~14 dB is achieved by intracavity spectral filtering of weak side modes using a narrow-band fiber Fabry–Perot etalon.

High power coherent two‐dimensional semiconductor laser array

Diffraction limited 1.4 W pulsed output power is demonstrated from a two‐dimensional 144 element surface emitting laser array placed in an external Talbot cavity. Phase locking of the array is achieved with a parallel phase sensing and control system based on phase contrast imaging used in combination with a liquid crystal array in the laser cavity. Diffraction limited cw operation is also demonstrated.

Broad-band wavelength tunable picosecond pulses from CW passively mode-locked two-section multiple quantum-well lasers

Wavelength tunable CW (continuous-wave) passive mode-locking of a two-section quantum-well laser coupled to an external cavity is demonstrated. A tuning range of 26 nm is achieved with typical autocorrelation full widths at half maximum of 4.5 ps. The pulses are not transform limited, having a typical time-bandwidth product of 2.5.<<ETX>>