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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Adjoint-Based Optimum Thermal Control of Pulsed Laser Diodes

Kenichi Morimoto
Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan

Yuji Suzuki
Department of Mechanical Engineering, The University of Tokyo Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

DOI: 10.1615/IHTC15.opt.009670
pages 5937-5946


KEY WORDS: Optimal control, Thermal management, Adjoint analysis, laser diodes

Abstract

The objective of the present study is to develop a versatile optimal control scheme for efficient suppression of high-speed temperature variation in pulsed laser diodes using an adjoint-based optimization method. In the present analysis, two different types of laser configuration are considered: edge-emitting laser (EEL) and surface-emitting laser (VCSEL). In both cases, Joule heating with a thin-film heater is employed as the control input in order to minimize the temperature change in a thin active region of the diode during the laser emission for ms. The control heater arranged on the top surface of the diode is assumed as planar for EEL and ring-shaped for VCSEL. Another heat input from an internal control heater is also considered for EEL. The present feedforward control scheme provides the optimum spatio-temporal heat-input distribution for a prescribed laser pulse, through adjoint-based heat-conduction analyses. We have formulated the present optimal control schemes and examined the effect of the heater arrangement on the present control. It is shown that the present control using an external control heater arranged on the top surface of the diode is effective for temperature control both in EEL and VCSEL. With the present control, the heat input from the control heater is applied prior to the onset of the laser emission, which suppresses the temperature variation by as much as 80%. It is found that the Fourier number of the layer between the control heater and the active region is the key parameter to minimize the temperature fluctuation.

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