Systems and methods for controlling the optical path length between a laser and an optical cavity
Inventors
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Publication Number
US-9581492-B2
Publication Date
2017-02-28
Expiration Date
Abstract
Systems and methods for controlling the optical path length between a feedback enabled laser and a cavity, and hence the optical feedback phase. A phasor element, positioned along an optical path between the laser and the cavity coupling mirror, includes a gas medium within a volume defined by the phasor element. The phasor element is configured to adjust or control an optical path length of the laser light between the laser and the cavity coupling mirror by adjusting or controlling a density of the gas medium within the phasor volume.
Core Innovation
The invention provides an optical feedback cavity-enhanced absorption spectroscopy system using a resonant optical cavity having at least two cavity mirrors, including a cavity coupling mirror, and a laser emitting laser light to be coupled into the cavity. A phasor element is positioned along an optical path between the laser and the cavity coupling mirror, where the phasor element includes a gas medium within a volume defined by the phasor element.
The phasor element is configured to adjust or control an optical path length of the laser light within the volume by adjusting or controlling a density of the gas medium within the volume. By changing the gas density, the system changes the optical path length and optical feedback phase, using pressure control and/or temperature control to change refractive index along the optical path without piezo actuators.
A detector measures intensity of light emerging from one of the cavity mirrors other than the cavity coupling mirror to generate a signal representing an intracavity optical power of light circulating in the cavity. The laser is sensitive to optical feedback, and continuous wave scanning or mean-frequency adjustment can be used to lock to cavity modes, supporting trace gas measurements.
Claims Coverage
The document includes two independent claims that share the core inventive concept of controlling an optical path length between a laser and a resonant optical cavity by adjusting the density of a gas medium in a phasor element, while measuring intracavity optical power from a non-coupling cavity mirror. The two independent claims cover an apparatus/system and a corresponding method, with inventive features centered on the cavity, laser coupling, phasor element gas-density path-length control, and cavity output detection.
Phasor element gas density controls optical path length
A phasor element positioned along an optical path between the laser and the cavity coupling mirror includes a gas medium within a volume defined by the phasor element, and is configured to adjust or control an optical path length of the laser light within the volume by adjusting or controlling a density of the gas medium within the volume.
Detector measures intracavity optical power from non-coupling mirror
A detector is configured to measure an intensity of light emerging from one of the at least two cavity mirrors other than the cavity coupling mirror and to generate a signal representing an intracavity optical power of light circulating in the cavity.
Resonant optical cavity with cavity coupling mirror
A resonant optical cavity having at least two cavity mirrors, one of which is a cavity coupling mirror, receives laser light from the laser.
Method coupling laser via cavity coupling mirror and adjusting gas-density path length
Coupling the laser light to the cavity via the cavity coupling mirror, adjusting an optical path length between the laser and the cavity coupling mirror by adjusting a density of a gas medium between the laser and the cavity coupling mirror, and measuring an intensity of light emerging from one of the at least two cavity mirrors other than the cavity coupling mirror and generating a signal representing an intracavity optical power of light circulating in the cavity.
Across the independent apparatus and method claims, the inventive coverage is directed to controlling laser-to-cavity optical path length by changing the density of a gas medium contained in a phasor element between the laser and the cavity coupling mirror, while deriving a signal proportional to intracavity optical power by measuring intensity from a cavity mirror other than the coupling mirror.
Stated Advantages
Not explicitly described in patent.
Documented Applications
trace gases (described as supported by trace gas measurements).
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