Theoretical and experimental analysis of the lateral modes of high-power broad-area lasers

Abstract

For maximum fiber-coupled power, broad-area (BA) diode lasers must operate with small lateral far field angles. However, these structures are laterally multi-moded, with low beam quality and wide emission angles. We use a combination of device simulation and diagnostic measurements to determine the physical factors limiting the lateral far field angle in state of the art BA lasers emitting at 975 nm. Two-dimensional simulations of the optical field enable the dominant lateral waveguiding mechanisms to be diagnosed. Spectrally resolved near and far field measurements will allow us to determine the nature of the lateral modes.

Basic Aspects of High-Power Semiconductor Laser Simulation

“…for two cases, without and with a temperature induced index profile due to self-heating. The stationary temperature profile has been calculated in advance by the tool JCMsuite [76], [81]. If the thermal lens is not taken into account, the far field profile is asymmetric.…”

“…The multi-peaked and not diffraction-limited lateral field profile of wide-aperture semiconductor lasers has been a long standing problem and has been investigated in the past by numerous authors [38], [71]- [74]. Although the broadening of the far field of continuous-wave operating lasers with increasing power can be at least partially attributed to the thermal lensing effect [58], [75], [76], a complete picture of the origin and mechanism has yet to be revealed. One mechanism is believed to be due to carrier induced antiguiding, i.e.…”

Experimental and theoretical analysis of the dominant lateral waveguiding mechanism in 975 nm high power broad area diode lasers

“…The currentinduced temperature increase, T, at each measurement point was calculated using the known values of thermal resistance, R th and power conversion efficiency, η C , and the associated peak refractive index change, n 0 , was derived assuming an average refractive index shift with temperature of 2.5 × 10 −4 K −1 [22]. A better approach would be to use models that can generate both the thermal and optical profiles, and this is currently under study [13]. A fully comprehensive model would lead to further increases in accuracy [34].…”

“…Although vertically single moded, these devices operate in multiple lateral modes, limiting how effectively they can be laterally collimated and fibre coupled [3][4][5][6][7][8][9][10][11][12][13]. The techniques necessary to significantly reduce this far field angle (and to improve the beam quality) continue to be intensively studied [1,2,10,11,[14][15][16][17].…”

Advanced finite-element methods for design and analysis of nanooptical structures: applications

“…Applications range from miniaturized light sources to energy-efficient lighting. In this field, JCMsuite is used to investigate and design optical properties of vertical cavity surface emitting lasers (VCSEL), 71 light emitting diodes (LED, OLED), 18,72 edge emitters, [73][74][75] plasmon lasers, 39,40 and other concepts. 68,[76][77][78][79][80][81] In the case of high-power devices, analysis should also include thermo-optical effects.…”