US 12,270,706 B2
Cavity enhanced absorption spectroscopy using a piecewise tunable laser and hierarchical wavelength determination
Alejandro Dario Farinas, Mountain View, CA (US); John A. Hoffnagle, San Jose, CA (US); Chris W. Rella, Sunnyvale, CA (US); and Sze Meng Tan, Santa Clara, CA (US)
Assigned to Picarro, Inc., Santa Clara, CA (US)
Filed by Picarro, Inc., Santa Clara, CA (US)
Filed on Aug. 15, 2021, as Appl. No. 17/402,571.
Application 17/402,571 is a continuation of application No. 16/714,518, filed on Dec. 13, 2019, granted, now 11,092,493.
Prior Publication US 2021/0372855 A1, Dec. 2, 2021
This patent is subject to a terminal disclaimer.
Int. Cl. G01J 3/433 (2006.01); G01N 21/39 (2006.01)
CPC G01J 3/4338 (2013.01) [G01N 21/39 (2013.01)] 5 Claims
OG exemplary drawing
 
1. Apparatus for performing cavity ring down spectroscopy, the apparatus comprising:
an optical source having a tunable emission wavelength, wherein the optical source has two or more tuning inputs, and wherein tuning of the optical source is piecewise continuous with respect to variation of any one of its tuning inputs;
an optical cavity having two or more mirrors and configured to accept an optical input from the optical source, wherein the optical cavity is also configured to accept a sample gas such that light circulating in the optical cavity passes through the sample gas;
a ringdown controller configured to monitor the light circulating in the optical cavity and configured to couple and interrupt coupling of light between the optical source and the optical cavity;
a tuning controller configured to tune the optical source in a setpoint mode and in a control mode;
wherein the control mode is closed-loop control of a single control input of the optical source to tune output wavelength of the optical source;
wherein the setpoint mode is an open-loop tuning of the optical source using all tuning inputs according to a lookup table configured to maximize a nonzero mode-hop free wavelength range around each output wavelength when using the control mode;
wherein the optical source is a sampled grating distributed Bragg reflector semiconductor laser.