Dispersion-compensated wavelength beam combining of quantum-cascade-laser arrays.

MIT Lincoln Laboratory, Lexington, Massachusetts 02420, USA.
Optics Express (Impact Factor: 3.53). 12/2011; 19(27):26725-32. DOI: 10.1364/OE.19.026725
Source: PubMed

ABSTRACT A multiwavelength array of distributed feedback (DFB) quantum cascade lasers (QCLs) that spans λ = 8.28 to 9.62 μm is wavelength beam combined (WBC) using both single-grating and dual-grating designs. WBC with a single grating results in a pointing error of 3-times the beam divergence for a single laser and arises from the nonlinear dispersion of the grating. By adding a second grating to compensate for the nonlinear dispersion, the pointing error is reduced to only 13% of the beam divergence for a single laser. A transceiver based on the dual-grating-WBC QCL was used to measure the transmittance of a polymer sheet placed between itself and a retroreflector over a round-trip distance of 70 meters.

Download full-text


Available from: Benjamin G Lee, Nov 20, 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we review the recent progress in broadly tunable single-mode mid-infrared quantum cascade lasers (QCLs). With a brief introduction on various applications of broadly tunable single-mode mid-infrared QCLs, we first categorize these lasers based on their configurations and tuning schemes. Then recent progress in each scheme is investigated, together with detailed discussions. Furthermore, the pros and cons of different approaches are compared, and the opportunities and challenges for future developments from our point of view are listed. Last but not least, potential new directions and prospects for obtaining broadly tunable singlemode characteristics are also provided. It is foreseeable that, with the development of high performance broadly tunable single-mode mid-infrared QCLs, more applications could be exploited in the near future with new phenomena to be discovered.
    Journal of optics 01/2015; 17(2):023001. DOI:10.1088/2040-8978/17/2/023001 · 2.01 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate active hyperspectral imaging using a quantum-cascade laser (QCL) array as the illumination source and a digital-pixel focal-plane-array (DFPA) camera as the receiver. The multi-wavelength QCL array used in this work comprises 15 individually addressable QCLs in which the beams from all lasers are spatially overlapped using wavelength beam combining (WBC). The DFPA camera was configured to integrate the laser light reflected from the sample and to perform on-chip subtraction of the passive thermal background. A 27-frame hyperspectral image was acquired of a liquid contaminant on a diffuse gold surface at a range of 5 meters. The measured spectral reflectance closely matches the calculated reflectance. Furthermore, the high-speed capabilities of the system were demonstrated by capturing differential reflectance images of sand and KClO<sub>3</sub> particles that were moving at speeds of up to 10 m/s.
    Optics Express 06/2014; 22(12):14392-14401. DOI:10.1364/OE.22.014392 · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report experimental demonstration of tunable, monolithic, single-mode quantum cascade lasers (QCLs) at ∼10 μm with a two-section etched slot structure. A single-mode tuning range of 77 cm−1 (785 nm), corresponding to ∼7.8% of the relative tuning range, was realized with a ∼20 dB side mode suppression ratio within the whole tuning range. Compared with integrated distributed feedback QCLs, our devices have the advantages of easy fabrication and a broader tuning range. Further theoretical analyses and numerical simulations show that it is possible to achieve a broad continuous tuning range by optimizing the slot structures. The proposed slot-waveguide design could provide an alternative but simple approach to the existing tuning schemes for realizing broadly continuous tunable single-mode QCLs.
    Applied Physics Letters 05/2014; 104(20):201106-201106-5. DOI:10.1063/1.4875711 · 3.52 Impact Factor