Patent ID: 6661941
Filing Date: 2003-12-09
Classification: G02B,H01S

Abstract:
A system, comprising:a laser configured to produce a laser beam at a laser frequency with a linear polarization and tunable to vary said laser frequency in response to a laser control signal; an optical coupler positioned to receive a portion of said laser beam and operable to split said received portion into a monitor beam and a first optical signal; an optical Fabry-Perot resonator configured to include a birefringent medium which exhibits different refractive indices a long first and second orthogonal polarization axes, and positioned to reflect a portion of said monitor beam as second optical signal and oriented so that said linear polarization of said monitor beam is not parallel to either of said first and said second polarization axes of said birefringent medium, wherein said resonator is configured to substantially transmit a first light beam in said monitor beam that is polarized in said first polarization axis and at a desired laser frequency and to substantially reflect a second light beam in said monitor beam that is polarized in said second polarization and at said desired laser frequency; a polarization unit located in an optical path of at least a portion of said second optical signal from said resonator to produce a phase shift of about 90 degrees between polarizations along said first and said second polarization axes in said portion of said second optical signal; an optical polarizer having a polarization that is not parallel to either of said polarizations along said first and said second polarization axes in said second optical signal, positioned to receive at least part of said portion of said second optical signal to produce a third optical signal; a first optical detector positioned to receive said first optical signal to produce a first detector signal; a second optical detector positioned to receive said third optical signal to produce a second detector signal; a signal subtracting circuit coupled to said first and said second optical detectors to mix said first and said second detector signals to produce an error signal that indicates a deviation of said laser frequency from said desired laser frequency; and a laser control unit coupled to receive said error signal and operable to produce said laser control signal according to said error signal which controls said laser frequency at said desired laser frequency.