Battery‐Operated Mid‐Infrared Diode Laser Frequency Combs

Abstract

Mid‐wave infrared (MIR, 3–5 µm) optical frequency combs (OFC) are of critical importance for spectroscopy of fundamental molecular transitions in space and terrestrial applications. Although in this band OFCs can be obtained via supercontinuum or difference frequency generation using optical pumping schemes, unprecedented source miniaturization, and monolithic design are unique to electrically‐pumped semiconductor laser structures. To date, high‐brightness OFC generation in this region has been demonstrated in quantum‐ and interband cascade lasers (QCL/ICL), yet with sub‐optimal spectral properties. Here, an MIR quantum well diode laser (QWDL) OFC is shown, whose excellent spectral uniformity, narrow optical linewidths, and milliwatt optical power are obtained at a fraction of a watt of power consumption. The continuously tunable source offers ≈1 THz of optical span centered at 3.04 µm, and a repetition rate of 10 GHz. As a proof‐of‐principle, a directly‐battery‐operated MIR dual‐comb source is shown with almost 0.5 THz of optical coverage accessible in the electrical domain in microseconds. These results indicate the high suitability of QWDL OFCs for future chip‐based real‐time sensing systems in the mid‐infrared.

Sub‐Nominal Resolution Fourier Transform Spectrometry with Chip‐Based Combs

“…To demonstrate the versatility of the technique and its independence on the comb source, we employed a recently demonstrated mid‐IR quantum well diode laser (QWDL) comb [ 35 ] at 3 $$\umu$$ m to probe two pure molecular standards: hydrogen cyanide (H$$^{12}$$ C$$^{14}$$ N), and acetylene ($$^{12}$$ C$$_2$$ H$$_2$$), at pressures of 2 Torr, and 10 Torr, respectively. Both analytes possess $$\approx$$ 340 MHz wide Doppler‐limited absorption lines (full width at half maximum, FWHM), which practically require an instrumental resolution greater than 100 MHz to accurately reproduce the lineshape.…”

“…The ICL comb device was a single‐section Fabry‐Pérot device with a 3 $$\umu$$ m wide ridge waveguide (Thorlabs) run without any frequency stabilization. The QWDL device described elsewhere [ 35 ] was analogously housed and biased, except for using a different laser driver due to the insufficient modulation range of the D2‐105‐500. In the latter case, an LDX‐3620, ILX Lightwave low‐noise laser driver capable of being modulated by tens of mA was used.…”

Asynchronous Upconversion Sampling of Frequency Modulated Combs

“…This included quantum cascade, [5] interband cascade, [6] quantum dot, [7] and quantum dash [8] lasers, but also conventional diode lasers. [9,10] Contrary to earlier observations, these frequency modulated sources were self-starting, without the need of having an intracavity phase modulator. With the emergence of these sources also temporal characterization techniques experienced a rebirth.…”

Sub-nominal resolution Fourier transform spectrometry with chip-based combs

“…The ICL comb device was a single-section Fabry-Pérot device with a 3 µm wide ridge waveguide (Thorlabs) run without any frequency stabilization. The QWDL device described elsewhere 30 was analogously housed and biased, except for using a different laser driver due to the insufficient modulation range of the D2-105-500. In the latter case, we used an LDX-3620, ILX Lightwave low-noise laser driver capable of being modulated by tens of mA.…”