Pressure and temperature tuning of laser diodes

Abstract

Pressure and temperature change the bandgap of III -V semiconductors and therefore they shift the gain spectrum of laser diodes. With 20 kbar pressure (achievable in a liquid pressure cell) we can increase the energy of the laser emission by about 200 meV for lasers grown on GaAs, InP, or GaSb. The main physical limitation of pressure tuning for shorter wavelengths (i.e. between 600 and 800 nm) is the reduction of indirect gap (Γ -X) in the barriers and claddings of the laser structure, leading to strong increase of leakage and threshold currents. In this wavelength range temperature tuning seems more practical. Cooling down the laser from room temperature (300 K) to about 100 K we should be able to increase the emission energy by about 80 meV. The combination of pressure/temperature tuning with tuning by external grating turned out to combine the merits of both methods: wide spectral range, narrow linewidth, stable emission wavelength. The method seems promising although several issues still have to be addressed like the reliability of lasers and pressure cells after multiple pressure cycles, stability of coupling between the laser diode and fiber under high pressure etc.

Electroluminescence in quantum well heterostructures p‐AlxGa1–xAs/GaAs1–yPy/n‐AlxGa1–xAs under uniaxial stress

“…Wavelength tuning was successfully demonstrated on semiconductor laser structures with external cavities in Littrow or Littman/Metcalf configuration [4] as well as using hydrostatic pressure up to P = 20 kbar [5,6]. Nevertheless, the development of cheap and simple devices for the wavelength tuning of laser diodes is a matter of particular interest.…”

Wide Range Wavelength Tuning of InGaAsP/InP Laser Diodes

“…Such tuning is limited to the range of positive net gain of the laser. Another method consists in shifting the whole gain spectrum of the laser by the application of high pressure or low temperature [2] (increased temperatures usually increase the threshold currents and decrease the efficiency). High pressure and low temperature increase the direct bandgaps in the active layer of the laser, shifting its emission to shorter wavelengths.…”

Pressure and Temperature Dependence of Threshold Current in Semiconductor Lasers Based on InGaAs/GaAs Quantum-Well Systems

“…Therefore the radiative recombination in the quantum well should constitute the major component of the threshold current in 980 nm devices. The experimental data have been obtained in the temperature range of 100-300 K and in the pressure range of 0-20 kbar [2]. They are compared with the predictions of a simple model that not only sheds light on the physical mechanisms of the pressure and temperature tuning of lasers but also gives fairly reasonable quantitative results.…”