Temperature distribution along the striped active region in high-power GaAlAs visible lasers

Todoroki, S.; Sawai, Masaaki; Aiki, K.

doi:10.1063/1.336125

Cited by 104 publications

(28 citation statements)

References 18 publications

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“…The use of Raman spectroscopy as a 'surface thermometer' for diode lasers has been pioneered by Todoroki et al [108]. Raman spectroscopy is an established analytical tool based on the analysis of scattered (external laser) light [109].…”

Section: Raman Spectroscopymentioning

confidence: 99%

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Mechanisms and fast kinetics of the catastrophic optical damage (COD) in GaAs‐based diode lasers

Tomm

Ziegler

Hempel

et al. 2011

Laser & Photonics Reviews

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Semiconductor lasers are the most efficient manmade narrow-band light sources and convert up to threequarters of electric energy into light. High-power diode lasers are characterized by very high internal power densities in their small cavity, resulting in local heating and sometimes device degradation. Catastrophic optical damage (COD) of diode lasers is a relevant degradation mechanism and limit for reaching ultrahigh optical powers. An overview is given on research activities targeting the mechanisms being relevant for the COD process in GaAs-based diode lasers emitting in the 630-1100 nm range. The discussion of experiments, where COD is artificially provoked, represents the main topic. The sequence of events and fast kinetics taking place on a nanosecond to microsecond time scale are addressed. A particular emphasis is laid on recent experimental work performed in the authors' laboratories. Paving the way for knowledge-based solutions towards more robust diode lasers represents the ultimate goal of this work. COD diagram determined for a batch of broad-area AlGaAs diode lasers. The time to COD within a single current pulse is plotted versus the actual average optical power in the moment when the COD takes place. Full circles stand for clearly identified COD events (right ordinate), whereas open circles (left ordinate) represent the pulse duration in experiments, where no COD has been detected. A borderline (gray) exists between two regions, i. e., parameter sets, of presence (orange) and absence of COD (blue). This borderline is somewhat blurred because of the randomness in filamentation of the laser nearfield and scatter in properties of the involved individual devices.

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Section: Raman Spectroscopymentioning

confidence: 99%

“…In their early paper [108], Todoroki et al reported facet temperatures of more than 200°C, a value that clearly exceeds any possible bulk temperature of an operating diode laser. Moreover, they presented first temperature profiles across facets, and explicitly pointed to the potential of microRaman spectroscopy for COD analysis.…”

Section: Raman Spectroscopymentioning

confidence: 99%

Mechanisms and fast kinetics of the catastrophic optical damage (COD) in GaAs‐based diode lasers

Tomm

Ziegler

Hempel

et al. 2011

Laser & Photonics Reviews

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“…Hence, it is very important to accurately evaluate the junction temperature and thermal resistance of UV devices. Several groups have reported the measurement of the junction temperature of LEDs and laser diodes using micro-Raman spectroscopy, 4) threshold voltage, 5) thermal resistance, 6) photothermal reflectance microscopy (PRM), 7) electroluminescence (EL), 8) photoluminescence (PL), 9) a noncontact method 10) and by using a nematic liquid crystal with infrared (IR) laser illumination.…”

Section: Introductionmentioning

confidence: 99%

Junction Temperature in Ultraviolet Light-Emitting Diodes

Gessmann

et al. 2005

Jpn. J. Appl. Phys.

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The junction temperature and thermal resistance of AlGaN and GaInN ultraviolet (UV) light-emitting diodes (LEDs) emitting at 295 and 375 nm, respectively, are measured using the temperature coefficient of diode-forward voltage. An analysis of the experimental method reveals that the diode-forward voltage has a high accuracy of ±3°C. A comprehensive theoretical model for the dependence of diode-forward voltage (V f) on junction temperature (T j) is developed taking into account the temperature dependence of the energy gap and the temperature coefficient of diode resistance. The difference between the junction voltage temperature coefficient (dV j/dT) and the forward voltage temperature coefficient (dV f/dT) is shown to be caused by diode series resistance. The data indicate that the n-type neutral regions are the dominant resistive element in deep-UV devices. A linear relationship between junction temperature and current is found. Junction temperature is also measured by the emission-peak-shift method. The high-energy slope of the spectrum is explored in the measurement of carrier temperature.

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“…However, the challenge is how to measure the delocalization effect on the temperature. Carrier temperature has been estimated indirectly and qualitatively using optoelectronic measurements and micro-Raman spectroscopy [20][21][22][23]. The success of an experimental verification of these predictions might lead to the design of new light harvesting nano devices, and in particular a solar nano refrigerator.…”

mentioning

confidence: 99%

Quantum confinement and negative heat capacity

Serra

Carignano

Alharbi

et al. 2013

EPL

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Thermodynamics dictates that the specific heat of a system is strictly non-negative. However, in finite classical systems there are well known theoretical and experimental cases where this rule is violated, in particular finite atomic clusters. Here, we show for the first time that negative heat capacity can also occur in finite quantum systems. The physical scenario on which this effect might be experimentally observed is discussed. Observing such an effect might lead to the design of new light harvesting nano devices, in particular a solar nano refrigerator.Thermodynamics dictates that the specific heat of a system is strictly non-negative, implying that the addition (subtraction) of energy cannot result in a decrease (increase) of the system's temperature [1]. Nevertheless there are well known cases where this rule is apparently violated [2,3]. For example, this phenomenom occurs at the nanoscale and it was eloquently showed by Schmidt et al. who, in an elegant series of experiments, determined a negative heat capacity of a Na cluster with 147 atoms for temperatures neighboring the melting temperature of the cluster [4][5][6]. Also at the astronomical scale negative heat capacities have been known for years [7], where it is observed that stars and star clusters increase their temperature as they age while loosing energy by radiation [8]. Therefore, invoking the thermodynamic limit is not sufficient to guarantee the equivalence of Canonical and Microcanonical ensembles. The key to theoretically reconcile these results with the thermodynamics was addressed by Thirring and coworkers: A system may display negative heat capacity, even in the thermodynamics limit, provided that it is not ergodic [9][10][11]. The ambiguity of negative heat capacity concept has been extensively examined by the work of RS Berry and coworkers [24][25][26][27][28][29] . In this letter we investigate whether this phenomenon could also be observed in the quantum domain, in particular, for small systems. An important motivation for the understanding and control of this phenomenon would be the implementation of refrigeration strategies at the nano scale, for example for light harvesting nano devices that would benefit from an inverted thermal response.Following previous ideas [12, 13] on a minimal model having negative specific heat for classical systems we study the effect of the delocalization of the wave function on the average kinetic energy of the system, and also on several definitions of temperature corresponding to the Canonical and Microcanonical statistics. Let us consider a 1d potential well trapped between impenetrable walls:This potential represents a simple example that suffices to show how a negative heat capacity emerges. The solution of the Schrödinger equation for one particle in V (x) given by Eq. (1) can be * kais@purdue.edu

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Temperature distribution along the striped active region in high-power GaAlAs visible lasers

Cited by 104 publications

References 18 publications

Mechanisms and fast kinetics of the catastrophic optical damage (COD) in GaAs‐based diode lasers

Mechanisms and fast kinetics of the catastrophic optical damage (COD) in GaAs‐based diode lasers

Junction Temperature in Ultraviolet Light-Emitting Diodes

Quantum confinement and negative heat capacity

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