Dr. Dirk A. Richter Profile

Dr. Dirk A. Richter

Research Engineer at Quanta3

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Author

Publications (7)

Proceedings Article | 26 January 2009 Paper

Airborne atmospheric research using mid-infrared laser spectroscopy

Alan Fried, Petter Weibring, Dirk Richter, James Walega

Proceedings Volume 7222, 722202 (2009) https://doi.org/10.1117/12.803634

KEYWORDS: Spectroscopy, Sensors, Spectroscopic atmospheric monitoring techniques, Mid-IR, Absorption, Signal detection, Interference (communication), Fiber lasers, Laser spectroscopy, Beam splitters

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Proceedings Article | 13 February 2008 Paper

Mid-infrared QPM laser sources for high-precision atmospheric trace gas measurements

Dirk Richter, Petter Weibring, Alan Fried, James Walega, Osamu Tadanaga, Masaki Asobe, Hiroyuki Suzuki

Proceedings Volume 6875, 68750J (2008) https://doi.org/10.1117/12.762294

KEYWORDS: Absorption, Mid-IR, Laser crystals, Crystals, Laser sources, Waveguides, Spectrometers, Sensors, Atmospheric sensing, Fiber lasers

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Proceedings Article | 25 October 2006 Paper

Tunable diode laser and difference frequency generation absorption spectrometers for highly sensitive airborne measurements of trace atmospheric constituents

Alan Fried, Petter Weibring, Dirk Richter, James Walega, Chad Roller, Frank Tittel

Proceedings Volume 6378, 63780F (2006) https://doi.org/10.1117/12.691318

KEYWORDS: Sensors, Absorption, Signal detection, Spectrometers, Mirrors, Tunable diode lasers, Difference frequency generation, Atmospheric sensing, Calibration, Semiconductor lasers

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Proceedings Article | 23 September 2002 Paper

Tunable optical fiber pumped difference frequency laser sources: state of the art

Dirk Richter, Alan Fried, Frank Tittel

Proceedings Volume 4817, (2002) https://doi.org/10.1117/12.452082

KEYWORDS: Mid-IR, Spectroscopy, Laser sources, Semiconductor lasers, Absorption, Optical fibers, Fiber lasers, Calibration, Optical amplifiers, Carbon monoxide

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Proceedings Article | 23 September 2002 Paper

Airborne measurements of formaldehyde employing a high-performance tunable diode laser absorption system

Alan Fried, Bryan Wert, James Walega, Dirk Richter, William Potter

Proceedings Volume 4817, (2002) https://doi.org/10.1117/12.452084

KEYWORDS: Absorption, Tunable diode lasers, Temperature metrology, Calibration, Hydrogen, Off axis mirrors, Absorbance, Laser systems engineering, Atmospheric chemistry, Oxidation

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Proceedings Article | 23 September 2002 Paper

Optimization of cw-QC lasers for Doppler and sub-Doppler molecular spectroscopy

James Kelly, Robert Disselkamp, Robert Sams, Thomas Blake, Steven Sharpe, Dirk Richter, Alan Fried

Proceedings Volume 4817, (2002) https://doi.org/10.1117/12.452124

KEYWORDS: Modulation, Quantum cascade lasers, Frequency modulation, Doppler effect, Fermium, Absorption, Amplitude modulation, Sensors, Spectroscopy, Signal to noise ratio

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Inter-subband (Type I) quantum-cascade (QC) lasers have shown the potential to generate tunable mid-IR radiation with narrow intrinsic linewidths (< 160 KHz in 15 mSec sweeps) and excellent amplitude stability (< 3 ppm averaged over minutes). Our bench-scale efforts to develop the Type I distributed feedback (DFB)-QC lasers for fieldable atmospheric chemistry campaigns, where multipass (Herriot or White) cells are used to enhance path-length, have not yet realized performance to the low intrinsic noise levels seen in these devices. By comparison, many operational systems' levels of noise-equivalent-absorbance (NEA) using Pb-salt lasers can routinely achieve at least one-order of magnitude better cw-performance, and with much lower powers. We have found that instability effets from weak back-scattered laser light -primarily from the Herriot cell- results in feedback-implicated technical noise well above the thermal and shot-noise of standard IR detectors. Of more fundamental concern is the fact that planar-stripe DFB-QC lasers undergo beam steering and transverse spatial-mode competitions during current tuning. It is the development of fully automated sub-ppbV sensitive IR chem-sensors. It is possible to reach low-ppm levels of absorptance change-detection (ΔI/I₀) over small wavelength regions with careful alignment to 100 M Herriott cells, but extreme care in spatial filtering is critical. However in the case of optical configurations which preclude significant optical feedback and need for stringent mode coupling alignments, the cw-DFB-QC lasers show great promise to do high resolution sub-Doppler spectroscopy. By serendipitous events, a varient of 'mode- or level-crossing' spectroscopy was probably rediscovered, which may allow very high resolution, sub-Doppler features and/or hyperfine alignments to be probed with 'uni-directional' topologies. We will primarily discuss the basic features of the 'uni-directional' sub-Doppler spectroscopy concept in this report. It shows potential to be exploitable in multi-pass cells or ring configurations. The phenomena of satuation 'dips' in molecular transitions appear to be very accessible with sinusoidally current-modulated DFB-QC lasers. Observations of sub-Doppler structures, either induced by residual AM 'pulsation dips' and/or hyperfine level-crossing effects (due to weak Zeeman splittings by the earth's B-field) can be recovered with good contrast. If this phenomena is indeed implicated with long-lived coherent hyperfine alignments, due perhaps to coherent population trapping in 'dark-states,' then sub-Doppler signals from saturated 'level-crossings' can potentially be seen without recourse to expensive polarization optics, nor elaborate beam shaping and isolation techniques.

Proceedings Article | 25 October 1999 Paper

Compact mid-infrared trace gas sensor based on difference frequency mixing

Frank Tittel, David Lancaster, Dirk Richter, Lew Goldberg, Jeffrey Koplow

Proceedings Volume 3758, (1999) https://doi.org/10.1117/12.366449

KEYWORDS: Sensors, Semiconductor lasers, Crystals, Gas sensors, Absorption, Fiber amplifiers, Mid-IR, Molecules, Calibration, Infrared spectroscopy

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