Quantum-dot laser produces multiple wavelengths for terahertz generation

March 5, 2012
A single quantum-dot (QD) laser diode developed by a group at the University of Dundee generates stable dual and/or multiple longitudinal modes in the near-infrared.

A single quantum-dot (QD) laser diode developed by a group at the University of Dundee (Dundee, Scotland) generates stable dual and/or multiple longitudinal modes in the near-infrared. The device has potential for production of terahertz radiation via optical difference-frequency generation.

Temperature-stabilized at 20°C, the laser diode is situated in an external-cavity setup containing two volume Bragg gratings (VBGs): one that selectively returns 1177 ±0.5 nm and 1182 ±0.5 nm wavelengths, and the other that selectively returns 1257 ±0.5 nm and 1262 ±0.5 nm wavelengths. The glass VBGs have an efficiency of about 15% and grating tilts of 1° to prevent backreflections. The difference frequencies for the two gratings are 0.946 ±0.019 THz and 1.078 ±0.021 THz, respectively.

When driven at a current of 70 mA, the laser emitted from the ground state (GS; matching VBG2); at 210 mA, excited-state (ES; matching VBG1) emission dominated the output. Intermediate currents produced a mix of GS and ES emission. Because each VBG is multiplexed (containing two gratings), a total of four wavelengths can be produced by the laser, with the relative output of each of two pairs adjustable by varying the current (the figure shows the output for a 150 mA current). In addition to photomixing for terahertz generation (and potentially two-color terahertz imaging), the laser is useful for spectroscopy. Contact Ross Leyman at [email protected].

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

Sponsored Recommendations

Demonstrating Flexible, Powerful 5-axis Laser Micromachining

Sept. 18, 2024
Five-axis scan heads offer fast and flexible solutions for generating precise holes, contoured slots and other geometries with fully defined cross sections. With a suitable system...

Enhance Your Experiments with Chroma's Spectra Viewer

Sept. 5, 2024
Visualize and compare fluorescence spectra with our interactive Spectra Viewer tool. Easily compare and optimize filters and fluorochromes for your experiments with this intuitive...

Optical Filter Orientation Guide

Sept. 5, 2024
Ensure optimal performance of your optical filters with our Orientation Guide. Learn the correct placement and handling techniques to maximize light transmission and filter efficiency...

Ensure Optimal Performance with Shortpass Filters

Sept. 5, 2024
Achieve precise wavelength blocking with our Shortpass Filters. Ideal for applications requiring effective light transmission and cutoff, these filters ensure optimal performance...

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!