Tunable Quantum Cascade Lasers and Photoacoustic Detection of Trace Gases, TNT, TATP and Precursors Acetone and Hydrogen Peroxide

• US 20110103412A1
• Filed: 11/01/2010
• Published: 05/05/2011
• Est. Priority Date: 06/23/2006
• Status: Abandoned Application

• Current Assignee: Alexei Tsekoun, C. Kumar N. Patel, Ilya Dunayevskiy, Manu Prasanna, Michael Pushkarsky, Richard Maulini, Rowel C. Go
• Original Assignee: Alexei Tsekoun, C. Kumar N. Patel, Ilya Dunayevskiy, Manu Prasanna, Michael Pushkarsky, Richard Maulini, Rowel C. Go
• Inventors: Prasanna, Manu, Pushkarsky, Michael, Patel, C. Kumar N., Maulini, Richard, Go, Rowel C., Dunayevskiy, Ilya, Tsekoun, Alexei
• Application Number:
  US12/917,406
• Publication Number:
  US 20110103412A1
• Time in Patent Office: Days
• US Class Current: 372/20
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: H01S 5/06255 Controlling the frequency of the radiation
• CPC Class Codes: H01S 5/0654 Single longitudinal mode emission
• CPC Class Codes: H01S 5/1092 Multi-wavelength lasing
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/3401 having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers

Abstract

Methods and apparatus for broad tuning of single wavelength quantum cascade lasers and the use of light output from such lasers for highly sensitive detection of trace gases such as nitrogen dioxide, acetylene, and vapors of explosives such as trinitrotoluene (TNT) and triacetone triperoxide (TATP) and TATP'"'"'s precursors including acetone and hydrogen peroxide. These methods and apparatus are also suitable for high sensitivity, high selectivity detection of other chemical compounds including chemical warfare agents and toxic industrial chemicals. A quantum cascade laser (QCL) system that better achieves single mode, continuous, mode-hop free tuning for use in L-PAS (laser photoacoustic spectroscopy) by independently coordinating gain chip current, diffraction grating angle and external cavity length is described. An all mechanical method that achieves similar performance is also described. Additionally, methods for improving the sensor performance by critical selection of wavelengths are presented.

Claims

1. A mechanical EGC system accommodating dispersion to optimize laser operation, comprising:

a diffraction grating synchronizing angular displacement of said diffraction grating with respect to an optical axis with linear displacement of said diffraction grating along said optical axis such that an integer number of half wavelengths are reflected to an end mirror for a selected wavelength transmitted to said end mirror by said diffraction grating along an optical axis;

a second projected axis orthogonal to said optical axis intersecting said optical axis at an intersection point behind said end mirror; and

said intersection point separated from said end mirror along said optical axis by a distance equal to a group optical length of a cavity distance between said diffraction grating and said end mirror and said actual cavity distance between said diffraction grating and said end mirror, said group optical length dependent upon linear dispersion of said cavity distance.