D. Lock

Direct measurement of facet temperature up to melting point and COD in high-power 980-nm semiconductor diode lasers

The authors describe a straightforward experimental technique for measuring the facet temperature of a semiconductor laser under high-power operation by analyzing the laser emission itself. By applying this technique to 1-mm-long 980-nm lasers with 6- and 9-/spl mu/m-wide tapers, they measure a large increase in facet temperature under both continuous wave (CW) and pulsed operation. Under CW operation, the facet temperature increases from /spl sim/25/spl deg/C at low currents to over 140/spl deg/C at 500 mA. From pulsed measurements they observe a sharper rise in facet temperature as a function of current (/spl sim/400/spl deg/C at 500mA) when compared with the CW measurements. This difference is caused by self-heating which limits the output power and hence facet temperature under CW operation. Under pulsed operation the maximum measured facet temperature was in excess of 1000/spl deg/C for a current of 1000 mA. Above this current, both lasers underwent catastrophic optical damage (COD). These results show a striking increase in facet temperature under high-power operation consistent with the facet melting at COD. This is made possible by measuring the laser under pulsed operation.

LED Junction Temperature Measurement Using Generated Photocurrent

LED-based lamps that are currently on the market are expensive due to the complex packaging required to dissipate the heat generated. This also limits their performance and lifetime due to the degradation of the phosphor or individual LED chips, in the case of RGB sources. There is a strong commercial imperative to develop in situ technology to measure and ultimately compensate for the thermal environment of a luminaire.

Carrier recombination in 1.3μm GaAsSb∕GaAs quantum well lasers

In this letter the authors present a comprehensive study of the threshold current and its temperature dependence in GaAsSb-based quantum well edge-emitting lasers for emission at 1.3 mu m. It is found that at room temperature, the threshold current is dominated by nonradiative recombination accounting for more than 90% of the total threshold current density. From high hydrostatic pressure dependence measurements, a strong increase in threshold current with pressure is observed, suggesting that the nonradiative recombination process may be attributed to electron overflow into the GaAs/GaAsP barrier layers and, to a lesser extent, to Auger recombination. (c) 2006 American Institute of Physics.

Spectroscopic characterization of 1450 nm semiconductor pump laser structures for Raman amplifiers

In order to characterize various different epilayer designs for semiconductor Raman amplifier pump lasers, combined electromodulated reflectance (ER) and photoluminescence (PL) studies were performed on wafer samples of InP / InGaAsP / InGaAsP edge-emitter laser structures in the infrared spectral region. Information about the quantum well (QW) transitions is obtained primarily from the ER, with additional corroboration provided by the PL. The ER spectra are fitted with a line shape model to obtain the ground-state and higher-order QW transition energies, which are found to agree well with theoretically calculated values. The ER spectra also provide the waveguide core and barrier compositions and built-in electric fields in the laser structures. The information provided by ER studies on the prefabrication wafers is found to corroborate well with diagnostic spontaneous emission measurements performed on actual laser devices fabricated from the same wafer batches.

Carrier recombination in 1.3 mu m GaAsSb/GaAs quantum well lasers

In this letter the authors present a comprehensive study of the threshold current and its temperature dependence in GaAsSb-based quantum well edge-emitting lasers for emission at 1.3 mu m. It is found that at room temperature, the threshold current is dominated by nonradiative recombination accounting for more than 90% of the total threshold current density. From high hydrostatic pressure dependence measurements, a strong increase in threshold current with pressure is observed, suggesting that the nonradiative recombination process may be attributed to electron overflow into the GaAs/GaAsP barrier layers and, to a lesser extent, to Auger recombination. (c) 2006 American Institute of Physics.

Carrier recombination in 1.3 μm GaAsSb/GaAs quantum well lasers

In this letter the authors present a comprehensive study of the threshold current and its temperature dependence in GaAsSb-based quantum well edge-emitting lasers for emission at 1.3 mu m. It is found that at room temperature, the threshold current is dominated by nonradiative recombination accounting for more than 90% of the total threshold current density. From high hydrostatic pressure dependence measurements, a strong increase in threshold current with pressure is observed, suggesting that the nonradiative recombination process may be attributed to electron overflow into the GaAs/GaAsP barrier layers and, to a lesser extent, to Auger recombination. (c) 2006 American Institute of Physics.

Carrier recombination in 1.3μmGaAsSb∕GaAs quantum well lasers

In this letter the authors present a comprehensive study of the threshold current and its temperature dependence in GaAsSb-based quantum well edge-emitting lasers for emission at 1.3 mu m. It is found that at room temperature, the threshold current is dominated by nonradiative recombination accounting for more than 90% of the total threshold current density. From high hydrostatic pressure dependence measurements, a strong increase in threshold current with pressure is observed, suggesting that the nonradiative recombination process may be attributed to electron overflow into the GaAs/GaAsP barrier layers and, to a lesser extent, to Auger recombination. (c) 2006 American Institute of Physics.

On the thermal stability of 1.3 /spl mu/m GaAsSb/GaAs-based lasers

In spite of the almost ideal variation of the radiative current of 1.3 mum GaAsSb/GaAs-based lasers, the threshold current, Jth, is high due to non-radiative recombination accounting for 90% Jth near room temperature. This also gives rise to low T0 values ~60 K close to room temperature, similar to that for InGaAsP/InP

Carrier recombination in InGaAs(P) Quantum Well Laser Structures: Band gap and Temperature Dependence

Using a combination of temperature and pressure dependence measurements, we investigate the relative importance of recombination processes in InGaAs‐based QW lasers. We find that radiative and Auger recombination are important in high quality InGaAs material. At 1.5μm, Auger recombination accounts for 80% Ith at room temperature reducing to ∼50% at 1.3μm and ∼15% at 980nm. We also find that Auger recombination dominates the temperature dependence of Ith around room temperature over the entire operating wavelength range studied (980nm–1.5μm).

Wavelength dependence of catastrophic optical damage threshold in 980 nm semiconductor diode lasers

We investigate the wavelength dependence of the catastrophic optical damage current in 980 nm lasers. Using high pressure and low temperature techniques, we find an intrinsic dependence of this threshold on wavelength.