Design of a solar-pumped semiconductor laser

Abstract

Since their first demonstration in 1962, solar-powered lasers have attracted interest as a tool for generating and distributing renewable energy. Proposals have ranged from orbiting solar laser power stations beaming energy down to terrestrial photovoltaic receivers, to arrays of solar lasers in desert areas linked to population centers via optical fibers. However, despite several decades of research, solar-powered lasers have yet to reach the levels of efficiency or output beam quality that would make these applications feasible. Here we propose a new solar laser architecture, the solar-pumped vertical external cavity surface emitting laser (SP-VECSEL), as a logical continuation of the proven mode-converting capabilities of diode-pumped VECSELs. In experiments using VECSEL gain samples pumped using sunlight, we demonstrate that no major drop in efficiency is observed beyond that associated with the quantum defect of the pump light, allowing us to predict that SP-VECSEL performance can substantially surpass that of existing solar lasers.

Detailed Balance Limit of Efficiency of Broadband-Pumped Lasers

“…For instance, in bandgap materials the absorption coefficient, α , below bandgap energy follows an exponential rule , where α 0 , E a are material constants and E U is the Urbach tail width 38 – 40 that scales as E U ∝ k B T . Hence in this particular case the tradeoff must be considered between the absorption constants ratio and the Stokes’ shift, since requiring at non-zero temperature leads to zero total efficiency due to infinite Stokes’ shift, while for the minimal Stokes’ shift the ratio is too low resulting in very high power threshold 41 .…”

A Review on Solar Secondary Concentrator

“…Figure 6. Side view for basic design of a DTIRC [31] DTIRC as a secondary concentrator has been widely used in various applications such as the pumping of power laser systems [32], concentrated photovoltaic (CPV) [14], and solar thermal application in space [33], [34]. Recently, Cruz-Silva et al [16] reformulate the Ning's formulation of DTIRC [31] to obtain an analytical framework for feasible designs which are easily implemented for computer numerical control (CNC) manufacturing and presented solar flux distribution in Linear Fresnel reflector (LFR) and parabolic through collector (PTC) using DTRIC as secondary concentrator.…”

Pumping of VECSELs using high quantum defect and broadband sources

“…Both lasing and photoluminescence measurements were made in order to find values of the internal quantum efficiency (IQE) of a VECSEL gain medium 7 . In the case of lasing measurements, similar VECSELs were constructed using an 11 quantum well, resonant, 1010 nm sample, pumped by either an 808 nm fiber coupled diode laser as a pump or using a 532 nm solid state laser.…”

“…They have therefore long been identified as having the potential to overcome the issues which limit the performance of existing solar lasers in terms of both efficiency and output beam quality 4, 5 , but only with the coming-of-age of high power CW VECSELs, featuring large pump spot areas and efficient thermal management, have semiconductor lasers been demonstrated which are compatible with solar pumping 6 . Two recent papers have identified VECSELs as having an architecture that is suitable for solar pumping 7,8 . In this paper we describe measurements of the efficiency of a VECSEL gain medium when pumped by large quantum defect sources and broadband sources, and discuss their impacts on the possible design and performance of a solar-pumped VECSEL.…”