Extended laser sensor

Claim 1

An optical sensor sensing various kinds of physical fields, comprising: a semiconductor diode lasing medium, with a first and a second end facet oriented perpendicularly to the optical axis of said medium, producing coherent optical energy at a lasing frequency, said first facet being highly reflective at the lasing frequency and said second facet being highly nonreflective at the lasing frequency; a fiber optic coupler with first, second, third and fourth ports for distributing optical energy incident on any one of said ports in predetermined ratios between the remainder of said ports a first optical fiber or first optical waveguide with a first end optically coupled to the second facet of said lasing medium and with a second end optically coupled to the first port of said coupler, said first optical fiber or said first optical waveguide transmitting optical energy between said lasing medium and said coupler; a resonant cavity having a response curve, said cavity including said fiber optic coupler a reference optical fiber or a reference optical waveguide with a first end optically coupled to the second port of said coupler, and a second highly reflective end; said cavity also including a sensing arm optical fiber or a sensing arm optical waveguide with a first end optically coupled to said third port of said coupler and with a highly reflective second end said resonant cavity replaces said second nonreflective facet and functions as a mirror of variable reflectivity such that said resonant cavity has a plurality of resonant modes where the frequencies of said modes are determined by the optical pathlength between the highly reflective ends of said reference and sensing fibers or waveguides and by the lasing frequency, and where the optical energy of said resonant modes is reflected back to said optical gain medium through said optical coupler and said first fiber or said first waveguide thereby exciting those lasing modes with frequencies within the peaks of the response curve of said resonant cavity; and means for varying the optical pathlength of said sensing optical fiber or said sensing optical waveguide in response to various kinds of incident physical fields of large spatial extent to shift the frequencies of said resonant modes.

Claim 9

A method for sensing various kinds of external fields, such as acoustic fields or magnetic fields, including the steps of: generating a coherent optical field in the lasing medium of a laser, said lasing medium having a plurality of lasing modes; coupling said optical output from said lasing medium into an optical resonant cavity having a response curve with a plurality of peaks; varying the frequency and phase of said resonant modes in response to a physical field of large spatial extent incident on a sensing arm in said resonant; reflecting the optical of said resonant cavity back into said lasing medium to excite only those lasing modes having frequencies within the peaks of the response curves of said resonant cavity.

Claim 10

A method for sensing various kinds of external fields, such as acoustic fields or magnetic fields, including the steps of: generating a coherent optical field in the lasing medium of a laser, said lasing medium having a plurality of lasing modes; coupling said optical output from said lasing medium into an optical resonant cavity having a response curve with a plurality of peaks; varying the frequency and phase of said resonant modes in response to a physical field of large spatial extent incident on a sensing arm in said resonant; reflecting the optical of said resonant cavity back into said lasing medium to excite only those lasing modes having frequencies within the peaks of the response curves of said resonant cavity.