Mid-IR instrument for analyzing a gaseous sample and method for using the same

• US 7,606,274 B2
• Filed: 03/13/2006
• Issued: 10/20/2009
• Est. Priority Date: 09/20/2001
• Status: Expired due to Term

• Current Assignee: The University Of Alabama At Birmingham Research Foundation
• Original Assignee: UAB Research Foundation (University of Alabama System)
• Inventors: Fedorov, Vladimir, Mirov, Sergey, Moskalev, Igor
• Primary Examiner(s): Harvey; Minsun
• Assistant Examiner(s): NIU, XINNING
• Application Number:
  US11/375,601
• Publication Number:
  US 20070064748A1
• Time in Patent Office: 1,317 Days
• Field of Search: 372 10- 17, 372/20, 372/23
• US Class Current: 372/20
• CPC Class Codes: C30B 29/48 AIIBVI compounds wherein A is Zn, Cd or Hg, and B is S, Se or Te
• CPC Class Codes: C30B 31/00 Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
• CPC Class Codes: C30B 31/02 by contacting with diffusion materials in the solid state
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01N 2021/1704 in gases
• CPC Class Codes: G01N 2021/399 Diode laser
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G02F 1/39 for parametric generation or amplification of light, infrared or ultraviolet waves
• CPC Class Codes: G02F 1/392 Parametric amplification
• CPC Class Codes: H01S 2301/04 Gain spectral shaping, flattening
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• CPC Class Codes: H01S 3/0604 in the form of a plate or disc
• CPC Class Codes: H01S 3/0627 the resonator being monolithic, e.g. microlaser
• CPC Class Codes: H01S 3/08009 using a diffraction grating
• CPC Class Codes: H01S 3/08086 Multiple-wavelength emission
• CPC Class Codes: H01S 3/094038 End pumping
• CPC Class Codes: H01S 3/094042 of a fibre laser
• CPC Class Codes: H01S 3/094061 Shared pump, i.e. pump light of a single pump source is used to pump plural gain media in parallel
• CPC Class Codes: H01S 3/09415 the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• CPC Class Codes: H01S 3/10092 : Coherent seed, e.g. injection locking
• CPC Class Codes: H01S 3/1055 : one of the reflectors being constituted by a diffraction grating
• CPC Class Codes: H01S 3/113 : using intracavity saturable absorbers
• CPC Class Codes: H01S 3/161 : holmium
• CPC Class Codes: H01S 3/162 : transition metal
• CPC Class Codes: H01S 3/1623 : chromium, e.g. Alexandrite
• CPC Class Codes: H01S 3/1628 : characterised by a semiconducting matrix
• CPC Class Codes: H01S 3/2308 : Amplifier arrangements, e.g. MOPA
• CPC Class Codes: H01S 3/2375 : Hybrid lasers H01S3/07 takes precedence
• CPC Class Codes: H01S 3/2383 : Parallel arrangements

Abstract

An optical nose for detecting the presence of molecular contaminants in gaseous samples utilizes a tunable seed laser output in conjunction with a pulsed reference laser output to generate a mid-range IR laser output in the 2 to 20 micrometer range for use as a discriminating light source in a photo-acoustic gas analyzer.

Claims

1. An optical nose system having a broadly tunable, narrow linewidth mid-IR laser source wherein the laser source has a modular structure and comprises

a) a tunable seed laser unit including a single-longitudinal mode, widely tunable TM²⁺:

II-VI master oscillator with a TM²⁺;

II-VI power amplifier having a laser output, where TM²⁺ stands for transition metal ion selected from the group consisting of Cr²⁺, Fe²⁺, Co²⁺ and Ni²⁺, and II-VI stands for ZnS, ZnSe, CdS, CdSe, ZnTe, CdTe and their mixtures wherein said seed laser is a broadly tunable single frequency laser without mode hoping which is comprised of Littrow or Littman dispersive cavity with accompanied by dynamic correction of cavity length;

b) a pulsed pump laser unit including a single-frequency, high energy, Q-switch laser having a laser output;

c) an Optical Parametric Generator-Amplifier, pumped by said pulsed pump laser unit and seeded by said seed tunable laser unit having a mid-IR output selectively variable over about 2 to 20 μ

m; and

wherein said pulsed pump and seed tunable lasers are pumped by a single diode, diode array, or fiber laser.

2. The optical nose system as defined in claim 1 wherein correction of cavity length is controlled by piezoelectric transducers.

3. The optical nose system as defined in claim 2 further comprising a Master Control Computer, single frequency pump pulsed laser unit with a wavelength locking, single frequency seed tunable laser unit with a feedback system for frequency stabilization, Optical Parametric Generator-Amplifier and wherein the length of said seed tunable laser cavity is controlled by a piezoelectric controller, a grating step motor driver connected to a step motor for diffraction grating or mirror of the tunable laser cavity, a wavelength controller operatively connected to send signals to said grating stepper motor driver dependant on inputs from said master control computer.

4. The optical nose system as defined in claim 3 wherein said Optical Parametric Generator-Amplifier is a difference frequency generator device where the laser radiations from the seed tunable laser unit and a high power pump laser unit are mixed in nonlinear crystal, selected from the group of ZGP, CdSe or GaSe.

5. The optical nose system as defined in claim 4 wherein the orientation of said nonlinear crystal is controlled by a rotation step motor receiving a control signal from said wavelength controller.

6. A method for analyzing a gaseous sample contained in a photoacoustic gas cell, said method comprising the steps of:

a) pumping a pulsed pump and tunable seed lasers and generating laser oscillation of the said lasers;

b) pumping optical parametric generator-optical parametric amplifier unit (OPG-OPA) with radiations of the pulsed pump and seed lasers and generating of tunable mid-IR signal and idler waves;

c) directing a tunable laser radiation from said OPG-OPA to the gas cell and measuring absorption spectrum; and

d) comparing the measured absorption spectrum with the known absorption spectra of the gaseous sample to determine the composition of the gaseous sample;

wherein

step a) further comprises;

Pumping of the said seed and pulsed pump lasers with Tm-fiber or Er-fiber pump lasers, and

step b) further comprises the step of

providing a ZGP nonlinear crystal in said OPG-OPA generating radiation over the 2-10 μ

m mid-IR spectral range,

rotating the position of said ZGP nonlinear crystal with a ZGP stepping motor,

providing a wavelength controller connected with a ZGP stepping motor,

calculating the required angle of rotation of the ZGP for the current wavelength, and

rotating the ZGP according to calculations.

7. A method for analyzing a gaseous sample contained in a photoacoustic gas cell, said method comprising the steps of:

a) pumping a pulsed pump and tunable seed lasers and generating laser oscillation of the said lasers;

b) pumping optical parametric generator-optical parametric amplifier unit (OPG-OPA) with radiations of the pulsed pump and seed lasers and generating of tunable mid-IR signal and idler waves;

c) directing a tunable laser radiation from said OPG-OPA to the gas cell and measuring absorption spectrum; and

d) comparing the measured absorption spectrum with the known absorption spectra of the gaseous sample to determine the composition of the gaseous sample, and

wherein step a) further includes;

generating a Q-switched Holmium laser radiation as a pump source for said OPG-OPA.

8. A method for analyzing a gaseous sample contained in a photoacoustic gas cell, said method comprising the steps of:

a) pumping a pulsed pump and tunable seed lasers and generating laser oscillation of the said lasers;

b) pumping optical parametric generator-optical parametric amplifier unit (OPG-OPA) with radiations of the pulsed pump and seed lasers and generating of tunable mid-IR signal and idler waves;

c) directing a tunable laser radiation from said OPG-OPA to the gas cell and measuring absorption spectrum; and

d) comparing the measured absorption spectrum with the known absorption spectra of the gaseous sample to determine the composition of the gaseous sample;

wherein

step a) further includes;

generating a Q-switched Erbium laser radiation as a pump source for said OPG-OPA, and

step b) further comprises the step of

providing a ZGP nonlinear crystal in said OPG-OPA generating radiation over the 2-10 μ

m mid-IR spectral range,

rotating the position of said ZGP nonlinear crystal with a ZGP stepping motor,

providing a wavelength controller connected with a ZGP stepping motor,

calculating the required angle of rotation of the ZGP for the current wavelength, and

rotating the ZGP according to calculations.

9. A method for analyzing a gaseous sample contained in a photoacoustic gas cell, said method comprising the steps of:

a) pumping a pulsed pump and tunable seed lasers and generating laser oscillation of the said lasers;

b) pumping optical parametric generator-optical parametric amplifier unit (OPG-OPA) with radiations of the pulsed pump and seed lasers and generating of tunable mid-IR signal and idler waves;

c) directing a tunable laser radiation from said OPG-OPA to the gas cell and measuring absorption spectrum; and

d) comparing the measured absorption spectrum with the known absorption spectra of the gaseous sample to determine the composition of the gaseous sample;

wherein step a) further comprises;

generating a single frequency tunable Cr²⁺;

II-VI laser radiation using a Cr²⁺;

II-VI master oscillator and Cr²⁺;

II-VI a power amplifier, where II-VI stands for Zn, Se, CdSe, ZnS, and their mixtures, and

transmitting said Cr²⁺;

II-VI widely tunable seed laser radiation to said OPG-OPA wherein said

Cr²⁺;

II-VI widely tunable seed laser radiation is continuously tunable over a 2-3.5 μ

m spectral range.

10. A method for analyzing a gaseous sample contained in a photoacoustic gas cell, said method comprising the steps of:

a) pumping a pulsed pump and tunable seed lasers and generating laser oscillation of the said lasers;

b) pumping optical parametric generator-optical parametric amplifier unit (OPG-OPA) with radiations of the pulsed pump and seed lasers and generating of tunable mid-IR signal and idler waves;

c) directing a tunable laser radiation from said OPG-OPA to the gas cell and measuring absorption spectrum; and

d) comparing the measured absorption spectrum with the known absorption spectra of the gaseous sample to determine the composition of the gaseous sample, and

wherein step b) further comprises the step of

providing a ZGP nonlinear crystal in said OPG-OPA generating radiation over the 2-10 μ

m mid-IR spectral range;

rotating the position of said ZGP nonlinear crystal with a ZGP stepping motor;

providing a wavelength controller connected with a ZGP stepping motor;

calculating the required angle of rotation of the ZGP for the current wavelength; and

rotating the ZGP according to calculations.

11. An optical nose system having a broadly tunable, narrow linewidth mid-IR laser source wherein the laser source has a modular structure and comprises

a) a tunable seed laser unit including a single-longitudinal mode, widely tunable TM²⁺:

II-VI master oscillator with a TM²⁺;

II-VI power amplifier having a laser output, where TM²⁺ stands for transition metal ion selected from the group consisting of Cr²⁺, Fe²⁺, Co²⁺ and Ni²⁺, and II-VI stands for ZnS, ZnSe, CdS, CdSe, ZnTe, CdTe and their mixtures;

b) a pulsed pump laser unit including a single-frequency, high energy, Q-switch laser having a laser output; and

,

c) an Optical Parametric Generator-Amplifier, pumped by said pulsed pump laser unit and seeded by said seed tunable laser unit having a mid-IR output selectively variable over about 2 to 20 μ

m, and

wherein said Optical Parametric Generator-Amplifier is a difference frequency generator device where the laser radiations from the seed tunable laser unit and a high power pump laser unit are mixed in nonlinear crystal, selected from the group of ZGP, CdSe or GaSe.

12. The optical nose system as defined in claim 11, further comprising a photo-acoustic cell receiving an optical input from said Optical Parametric Generator-Amplifier for analyzing a gaseous sample.