Room-temperature mid-infrared interband cascade vertical-cavity surface-emitting lasers

Abstract

We report interband cascade vertical-cavity surface-emitting lasers (ICVCSELs) that operate in pulsed mode at temperatures up to 70 °C. Their emission at λ ≈ 3.4 μm extends considerably the previous longest wavelength of 3.0 μm for an electrically-pumped vertical-cavity surface-emitting laser operating at room temperature. The output from mesas having diameters ranging from 30 to 60 μm (with emission aperture diameters of 20–50 μm) is circularly symmetric, and the threshold current densities at T = 25 °C are as low as 390 A/cm2. However, the differential slope efficiencies are low, e.g., ≤50 mW/A at T = 25 °C, due to loss in the top and bottom mirrors and reduced current efficiency. The smallest device operates in a single spectral mode despite having an emission aperture much wider than the wavelength.

The Interband Cascade Laser

“…While an ICVCSEL was originally designed and its performance predicted over two decades ago [26], the first experimental demonstration was not accomplished until 2016 by NRL [144]. The structure illustrated in Figure 16 had 15 active stages that were divided into three groups positioned at antinodes of the resonant optical field.…”

Substrate-emitting ring interband cascade lasers

“…We fabricated a second-order DFB grating into the upper cladding layers and subsequently filled the etched grooves with metal. The measured output power and the slope efficiency are higher than those obtained with interband VCSEL devices 14,15 but still considerably lower than from edge-emitting DFB ICLs. 5 The ring ICL device is limited to pulsed operation due to poor heat dissipation capabilities.…”

“…In addition, surface emission enables two-dimensional array integration of multiple devices. Recently, an electrically pumped interband cascade vertical-cavity surface-emitting laser (VCSEL) has been demonstrated 14 in pulsed operation at a wavelength of k % 3.4 lm. Another VCSEL device 15 that is based on a single stage active region design (k ¼ 4 lm) operated in continuous-wave up to -7 C and in pulsed mode up to 45 C. For these devices, the feedback mechanism is provided by high-quality Bragg mirrors grown below and above the ICL gain material.…”

“…The extracted differential slope efficiency for the ring ICL is 104 mW/A at 20 C, which corresponds to an external differential quantum efficiency of $31%. In comparison, a single-stage VCSEL device 15 with a buried tunnel junction (12 lm aperture size) showed a maximum slope efficiency of 26 mW/A at -40 C. A 15-stage interband cascade VCSEL 14 with 60/40 lm mesa/ aperture diameter reached $52 mW/A at 20 C. Furthermore, the output power of ring ICLs can be scaled by changing the diameter and width of the waveguide. The relatively small gain volume in VCSELs on the one hand limits the maximum output power, but it also enables to build surface-emitting and inherent single-mode devices 28 without any diffraction grating.…”

Mid-Infrared Tunable Laser-Based Broadband Fingerprint Absorption Spectroscopy for Trace Gas Sensing: A Review

“…The buried tunnel junction (BTJ) concept yields high-performance VCSELs in the wavelength ranges of 1.3-2.6 µm [75] and 2.3-3.0 µm [76], respectively. An interband cascade VCSEL has achieved lasing to λ~3.4 µm in pulsed mode at temperatures up to 70 • C [77], and a 4 µm VCSEL has been developed by using a single-stage active region with eight type-II quantum wells combined with BTJ technology [78]. VCSELs operate with very low threshold currents of several mA and very low power consumption of milliwatts.…”