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1

Application of spatially resolved thermoreflectance for the study of facet heating in high power semiconductor lasers

Bugajski M., Ochalski T., Piwonski T., Wawer D.

Optica Applicata

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2006

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Vol. 36, nr 2-3

339-349

EN

We have developed a new technique for monitoring the facet heating in semiconductor lasers and for correlating these measurements with the performance and reliability of the device. The method is based on thermoreflectance, which is a modulation technique relying on periodic facet temperature modulation induced by pulsed current supply of the laser. The periodic temperature change of the laser induces variation of the refractive index and consequently modulates the probe beam reflectivity. The technique has a spatial resolution of about 1 m and temperature resolution better than 1 K, and can be used for temperature mapping over a 300 m × 300 m area. It can be applied to any kind of edge emitting lasers or laser bars. The technique is crucial for understanding the thermal behavior of a device.

2

Thermoreflectance study of temperature distribution on the semiconductor laser mirrors

Piwoński T., Wawer D., Szymański M., Ochalski T., Bugajski M.

Optica Applicata

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2005

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Vol. 35, nr 3

611-617

EN

In the high power semiconductor lasers, the surface of the mirror is the key element of the construction, which has the main impact on the reliability and degradation processes. In the case of lasers fabricated with the use of GaAs compounds the highest power emitted by the structure is limited by the catastrophic optical damage (COD) effect due to increase of temperature on the air-semiconductor edge. The technique which enables examining the temperature distribution on the mirror surface is thermoreflectance. In this paper, we present the technique of temperature mapping on the mirror surface of the high power semiconductor lasers based on the thermoreflectance method.

3

Thermoreflectance and micro-Raman measurements of the temperature distributions in broad contact laser diodes

Ochalski T. J., Piwoński T., Wawer D., Pierściński K., Bugajski M., Kozłowska A., Maląg A., Tomm J. W.

Optica Applicata

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2005

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Vol. 35, nr 3

479-484

EN

In this paper we describe a number of optical techniques suitable for estimation of the semiconductor surface temperature. High spatially resolved thermoreflectance will be shown as a powerful tool to measure temperature distribution at the laser diode front facet. For determination of the absolute value of the front facet temperature we use micro-Raman spectroscopy. Both techniques will be presented as a complementary ways to determine surface temperature distribution on the working laser diode.

4

Analysis of mounting induced strain in semiconductor structures by means of spatially resolved optical modulation techniques

Pierściński K., Piwoński T., Ochalski T. J., Kowalczyk E., Wawer D., Bugajski M.

Optica Applicata

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2005

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Vol. 35, nr 3

605-610

EN

A wide range of applications of high-power diode lasers is connected with the tendency towards device miniaturization resulting in increased power densities. To manage the thermal load, the chips or arrays of chips (the so-called laser lines or cm-bars) have to be mounted with low thermal resistance on a heat sink of high thermal conductivity. These measures potentially introduce mechanical strain and defects into the semiconductor chips affecting the parameters of laser emission, e.g., spectral position. The ability of optical modulation techniques to monitor spatial strain distribution along the devices was evaluated.

5

Analysis of high-power diode laser thermal properties by micro-Raman spectroscopy

Wawer D., Tomm J. W., Pierściński K., Bugajski M.

Optica Applicata

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2005

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Vol. 35, nr 3

555-560

EN

Spatially resolved micro-Raman measurements have been performed to determine temperature distribution over the facet of high power semiconductor diode lasers. This technique is non-invasive and allows one to study the local temperature on the surface of the mirror of semiconductor diode lasers under normal operating conditions. The micro-Raman measurements can also serve as a calibration of absolute temperature for the other contact-less thermometric methods, e.g., thermoreflectance.

6

High power QW SCH InGaAs/GaAs lasers for 980-nm band

Bugajski M., Mroziewicz B., Regiński K., Muszalski J., Kosiel K., Zbroszczyk M., Ochalski T., Piwoński T., Wawer D., Szerling A., Kowalczyk E., Wrzesińska H., Górska M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2005

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Vol. 53, nr 2

113-122

EN

Strained layer InGaAs/GaAs SCH SQW (Separate Confinement Heterostructure Single Quantum Well) lasers were grown by Molecular Beam Epitaxy (MBE). Highly reliable CW (continuous wave) 980-nm, broad contact, pump lasers were fabricated in stripe geometry using Schottky isolation and ridge waveguide construction. Threshold current densities of the order of Jth = 280 A/cm2 (for the resonator length L = 700 [mu]m) and differential efficiency [eta]= 0.40 W/A (41%) from one mirror were obtained. The record wall-plug efficiency for AR/HR coated devices was equal to 54%. Theoretical estimations of above parameters, obtained by numerical modelling of devices were Jth = 210 A/cm and [eta] = 0.47 W / A from one mirror, respectively. Degradation studies revealed that uncoated and AR/HR coated devices did not show any appreciable degradation after 1500 hrs of CW operation at 35°C heat sink temperature at the constant optical power (50 mW) conditions.

7

Reflectance study of SiO2/Si3N4 dielectric Bragg reflectors

Szerling A., Wawer D., Hejduk K., Piwoński T., Wójcik A., Mroziewicz B., Bugajski M.

Optica Applicata

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2002

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Vol. 32, nr 3

523-527

EN

We present the results of reflectance investigations into SiO2/Si3N4 dielectric distributed Bragg reflectors (DBR). The dielectric multilayers forming reflectors have been deposited by plasma enhanced chemical vapour deposition (PECVD) on silicon substrates. Such structures can be utilised in vertical cavity surface emitting lasers (VCSELs) and resonant cavity light emitting diodes (RC LEDs)