High-power, high-brightness continuous-wave interband cascade lasers with tapered ridges

Abstract

We report tapered-ridge mid-infrared (λ = 3.75 μm) interband cascade lasers emitting up to 403 mW of continuous wave output power at T = 25 °C, with beam quality characterized by M2 = 2.3. One index-guided tapered structure consisted of a single 4-mm-long section with ridge width varying linearly from 5 μm to 63 μm. Another device that combined a narrow ridge of uniform width with a tapered section produced slightly lower maximum output power and brightness.

Interband cascade lasers with high CW power and brightness

“…11 A tapered ICL subsequently emitted more power (403 mW) with similar beam quality, for a higher net brightness. 12 While all of these previous narrowridge ICLs investigated by NRL have emitted within a standard spectral range of 3.7-3.9 μm, similar performance would have been expected at any wavelength between 3.2 μm and about 4.1 μm, based on the pulsed performance of broad-area devices fabricated from a wide variety of wafers. 6 In parallel with the design improvements that have accounted in part for the recent advances in cw performance, other ongoing efforts have sought to refine the methods for processing ICL narrow ridges.…”

“…Figure 5 shows representative cw far-field intensity profiles, measured along the slow axis at 25 °C, for 22-μm-wide ridges with corrugated sidewalls that were etched with methane (a) and BCl 3 (b). The "effective M 2 " 12,16,17 values extracted from the profiles are indicated in the figure for each current. At the highest output powers, the resulting M 2 values ranged from 2.3 for a 22-μm-wide ridge etched with BCl 3 to 3.7 for a 32-μm-wide ridge etched with methane.…”

Influence of carrier concentration on properties of InAs waveguide layers in interband cascade laser structures

“…Although ICLs based on GaSb substrates reached exceptional operating parameters, i.e. low threshold currents and small electrical power consumption 3,4 , operation far above room temperature 5,6 in the 3 -5.5 µm range, several active region's modifications have been studied in order to tailor the emission wavelength deeper into the mid-infrared and to provide enhancement for the oscillator strength of the active optical transition: i) increasing the InAs layer width 7 ; ii) incorporation of arsenic atoms into GaInSb resulting in a quaternary GaInAsSb layer for the confinement of holes 8,9 ; iii) modification of the standard W-shaped InAs/GaInSb/InAs quantum well by application of additional InAs and…”

Type-II quantum wells with tensile-strained GaAsSb layers for interband cascade lasers with tailored valence band mixing

“…4 The interband cascade lasers (ICLs) 5,6 have been shown as efficient laser sources for such applications. This was enabled due to their single mode, continuous wave and high power operation at room or even elevated temperatures, 7,8 broad spectral tunability, 9 and low threshold currents resulting in low power consumption. 10 On the other hand, however, there are still some unresolved issues and space for improvement, where apparently new designs and new material solutions are demanded.…”