Photoacoustic spectra of ammonia and water vapor were recorded by use of a continuous-wave quantum-cascade distributed-feedback (QC-DFB) laser at 8.5 mum with a 16-mW power output. The gases were flowed through a cell that was resonant at 1.6 kHz, and the QC-DFB source was temperature tuned over 35 nm for generation of spectra or was temperature stabilized on an absorption feature peak to permi...

We report a novel laser cavity design in third-order distributed feedback (DFB) terahertz quantum-cascade lasers based on a perfectly phase-matching technique. This approach substantially increases the usable length of the third-order DFB laser and leads to narrow beam patterns. Single frequency emissions from 151 apertures (5.6 mm long device) are coherently added up to form a narrow beam with...

Milliwatt average power terahertz quantum cascade lasers (THz-QCLs, 2 THz to 5 THz) have been developed for spectroscopy and as local oscillators for heterodyne receivers. Novel DFB THz-QCLs have been fabricated and show single-mode operation. The narrow line widths of <10 MHz and stark shift tuning of of 6 GHz, allows for wavelength modulation spectroscopy of low pressure gasses in the unexplo...

This article analyzes compact laterally coupled distributed feedback DFB lasers with three defect regions. These devices are more flexible and smaller than conventional DFB lasers, having typical lengths between 20 and 50 m and a width less than 1 m lateral gratings are inserted in a single-mode waveguide . We optimize the defect regions to achieve an improved performance. In other words, an ad...

There is an increasing need in many chemical sensing applications ranging from industrial process control to environmental science and medical diagnostics for fast, sensitive, and selective gas detection based on laser spectroscopy. The recent availability of novel pulsed and CW quantum cascade distributed feedback (QC-DFB) lasers as mid-infrared spectroscopic sources address this need. A numbe...

Results are presented on laterally-coupled distributed feedback (LC-DFB) ridge laser diodes. The cpitaxial regrowth required in most distributed feedback devices is eliminated by using lateral evanescent coupling of the field to gratings etched along the sides of the ridge. A pulsed single-mode output power of 36 mW per facet was achieved at 937.5 nm with a sidemode suppression ratio (SMSR) of ...

In this paper, we explore a novel approach to enhancing fingerprint images using a new binary directional filter bank (DFB). Automated fingerprint identification systems (AFIS) are used to classify a fingerprint in a large volume of images. Many approaches to AFIS have been suggested, most sharing in common the idea of extracting discriminate feature representations. As part of that process, th...

This paper presents a new technique to generate microwave signal using an electro-absorption modulator (EAM) integrated with a distributed feedback (DFB) laser subject to optical injection. Experiments show that the frequency of the generated microwave can be tuned by changing the wavelength of the external laser or adjusting the bias voltage of the EAM. The frequency response of the EAM is stu...

We demonstrate the transmission of uncompressed 4K videos over photonics-based terahertz (THz) wireless link using a directly modulated distributed feedback laser diode (DFB-LD). For optical heterodyne mixing and data modulation, DFB-LD was employed with 5.94-Gb/s non-return-to-zero signal, which is related to 6G-serial digital interface standard support ultra-high-definition video resolution. ...

Monolithically integrated four-channel distributed feedback (DFB) laser array has been fabricated by metal organic vapor phase epitaxy (MOVPE) selective area growth for 1.55μm coarsewavelength division multiplexing (CWDM) systems. Wide-stripe MOVPE selective area growth and electron-beam lithography are used to obtain wide CWDM channel spacing of 20 nm. Optical outputs from the simultaneously b...