Richard Cendejas

Quantum cascade lasers with voltage defect of less than one longitudinal optical phonon energy

Efficient use of applied voltage in quantum cascade (QC) lasers is a critical factor in achieving high wall-plug efficiency and low compliance voltage. We demonstrate a QC laser emitting at 4.2 μm featuring a low voltage defect and short injector with only four quantum wells. Devices with a voltage defect of 20 meV, well below the energy of the longitudinal optical phonons, and a voltage efficiency of 91%, a record value for QC lasers, are reported for pulsed operation at 180 K. Voltage efficiencies of greater than 80% are exhibited at room temperature. Overall performance showed wall-plug efficiencies ranging from 21% at cryogenic temperatures to 5.3% at room temperature.

Wavelength selection for quantum cascade lasers by cavity length

A systematic shift in spectral emission wavenumbers in quantum cascade lasers (QCLs) is observed over a variation in cavity lengths from 0.5 to 3 mm resulting in a gain peak shift ranging from 2404 to 2286 cm−1. Thereby, a wavelength selection range of 118 cm−1 is provided, which is sufficiently broad for selecting the laser emission across the entire CO2 absorption band at 2326 cm−1 (4.3 μm). In contrast to current QCL wavelength selection techniques, modifying the cavity length is a straightforward postprocessing procedure. Experimental evidence confirms that this frequency shift is due to a change in threshold voltage and applied electric field as a function of cavity length which is in agreement with the theory.

Cavity Length Scaling of Quantum Cascade Lasers for Single-Mode Emission and Low Heat Dissipation, Room Temperature, Continuous Wave Operation

Single-mode operation of Fabry-Perot quantum cascade (QC) lasers is achieved through the systematic shortening of the cavity length from 764 to 110 μm. The increased mirror loss is mitigated using highly reflective (HR) metallic facet coatings (R >; 95%). Ultrashort cavity QC lasers operate single mode with the best device having a mode-hop free current tuning range of 3.44 cm-1. Using combined heat-sink temperature and current tuning, the largest single-mode tuning range attained was 8.56 cm-1. The heat dissipation of a 110-μm ultrashort cavity QC laser is 0.23 W at 80 K and 0.43 W at 150 K. With a 500-μm cavity and both facets HR coated with reflectivities of ~95% and 75%, room-temperature continuous wave operation is realized with heat dissipation of 1.2-1.7 W.

Single-mode, narrow-linewidth external cavity quantum cascade laser through optical feedback from a partial-reflector.

An external-cavity (EC) quantum cascade (QC) laser using optical feedback from a partial-reflector is reported. With this configuration, the otherwise multi-mode emission of a Fabry-Perot QC laser was made single-mode with optical output powers exceeding 40 mW. A mode-hop free tuning range of 2.46 cm(-1) was achieved by synchronously tuning the EC length and QC laser current. The linewidth of the partial-reflector EC-QC laser was measured for integration times from 100 μs to 4 seconds, and compared to a distributed feedback QC laser. Linewidths as small as 480 kHz were recorded for the EC-QC laser.

Tunability of notch angles in quantum cascade microlasers with highly deformed spiral resonators

We study the spectral characteristics of spiral-shaped micro-cylindrical quantum cascade lasers with various spiral geometries. With medium deformations and notch angles, our lasers can achieve single-mode emission with a side-mode suppression ratio over 30 dB.

Advancements and challenges for photonic components for avionic interconnects

We have designed and fabricated ultra-low noise, high power laser source and high dynamic range receiver for RF over fiber. Links with Noise Figure of less than 5dB have been measured and dynamic range dependence on link gain investigated. RF optical links were tested successfully in an ESM system.

Quantum cascade lasers for sensing CO 2 isotopic fingerprints

We demonstrate a quantum cascade laser for detecting 12CO 2 and 12CO 2 isotopes for use in fingerprinting CO 2 emissions from sources such as power plants and carbon storage reservoirs. The lasers emit a single mode at 4.22 μm in continuous wave operation.

Quantum cascade microlasers with highly deformed spiral-resonators

We study the spectral characteristics of spiral-shaped micro-cylindrical quantum cascade lasers with various spiral geometries. With medium deformations and notch angles, our lasers can achieve single-mode emission with a side-mode suppression ratio over 30 dB.