Sagnac fourier transform spectrometer having improved resolution

A Sagnac interferometer, comprising

• a beamsplitter arranged to receive an input beam of light having different wavelengths λ1 and λ2, and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• a first grating arranged so as to diffract the first beam, said first grating oriented to provide a first incident angle and a first diffraction angle for the wavelength, λ1, and to provide a first incident angle and a first diffraction angle for the wavelength, λ2, in said first beam, the first diffraction angle for both of said wavelengths, λ1 and λ2, depending on the respective first incident angles and the respective wavelengths;
• a second grating arranged so as to diffract the first beam after being diffracted by the first grating, said second diffraction grating oriented to provide a second incident angle and a second diffraction angle for said wavelength, λ1, and to provide a second incident angle and a second diffraction angle for said wavelength, λ2, such that said second incident angle for both of said wavelengths, λ1 and λ2, depends on the respective first diffraction angles, and the second diffraction angle for both of said wavelengths, λ1 and λ2, depends on the respective second incident angles and the respective wavelengths,
• an odd number of mirrors between the first and second gratings;
• and
• wherein said first and second gratings are oriented so that the second diffraction angle for the wavelength, λ1, is different from the second diffraction angle for the wavelength, λ2, the difference including (i) a first contribution caused by the difference in the respective wavelengths on the diffraction of the first beam by the second grating and (ii) a second contribution caused by a difference in the respective second incident angles resulting from the difference in the respective first diffraction angles, said first contribution reinforcing the second contribution.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having a wavelength and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• a first grating disposed in said first optical path such that said first beam is incident upon said first grating at a first incident angle, said first grating diffracting said first beam by a first diffraction angle, the first incident angle and the first diffraction angle being displaced to the same side of a line normal to the first grating;
• and
• a second grating disposed in said first optical path to diffract said first beam by a second diffraction angle after being diffracted by the first grating,
• wherein said first and second gratings are configured such that first and second optical beams in said output beam path have an angular separation that is larger than either a first amount of angular separation caused by the first grating, or a second amount of angular separation caused by the second grating.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having a wavelength and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• a first grating disposed in said first optical path to diffract said first beam by a first angle;
• a second grating disposed in said first optical path to diffract said first beam by a second angle after being diffracted by the first grating;
• and
• at least one mirror disposed in said first and second optical paths between the first and second gratings,
• wherein said first and second gratings are configured such that first and second optical beams in said output beam path have an angular separation that is larger than either a first amount of angular separation caused by the first grating, or a second amount of angular separation caused by the second grating.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having at least one wavelength and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• a first grating disposed in said first optical path so as to diffract the first beam;
• and
• a second grating disposed in said first optical path to diffract the first beam after being diffracted by the first grating, said first and second gratings further disposed in said second optical path to diffract said second optical beam,
• wherein said first and second gratings are oriented so as to satisfy the principle of reinforcement, and wherein the first and second paths comprise at least one diffractive order of said first and second gratings that is greater than the ±1 diffractive order.

A Sagnac interferometer, comprising:

• means for splitting an input beam of light having at least one wavelength into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• first means for diffracting said first beam at a diffraction angle that is displaced to the same side of a line normal to a surface of said first means where said first beam is incident upon said first means;
• and
• second means for diffracting said first beam after being diffracted by the first diffracting means,
• wherein said first and second diffracting means satisfy the principle of reinforcement.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having a wavelength and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• a plurality of gratings disposed in said first path so as to diffract said first optical beam by a first angle, said plurality of gratings further disposed in said second optical path so as to diffract said second optical beam by a second angle,
• wherein said plurality of gratings is arranged such that said first and second beams are combined parallel to one another in a reference direction if their wavelength is equal to a reference wavelength,
• wherein, if the wavelength of the first and second beams is not equal to the reference wavelength, said first beam is outputted in a first direction and said second beam is outputted in a second direction, said plurality of gratings being arranged such that when said first and second optical beams are combined, the angular separation between said first and second optical beams is larger than the absolute value of the angle between the first direction and the reference direction, and larger than the absolute value of the angle between the second direction and the reference direction, and
• wherein the first and second paths comprise at least one diffractive order of said plurality of gratings that is greater than the ±1 diffractive order.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having a wavelength and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• a plurality of gratings disposed in said first path so as to diffract said first optical beam a first angle, said plurality of gratings further disposed in said second optical path so as to diffract said second optical beam at a second angle;
• and
• one or more mirrors disposed in said first and second paths between any two of said plurality of gratings,
• wherein said plurality of gratings satisfy the principle of crossing.

A Sagnac interferometer, comprising:

• means for splitting an input beam of light into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• means for diffracting said first optical beam and said second optical beam, said means for diffracting comprising more than two diffractive surfaces,
• wherein said diffracting means are arranged such that said first and second optical beams are combined parallel to one another in a reference direction if their wavelength is equal to a reference wavelength, and
• wherein, if the wavelength of the first and second optical beams is not equal to the reference wavelength, said first optical beam is outputted in a first direction and said second optical beam is outputted in a second direction, said diffracting means being arranged such that when said first and second optical beams are combined, the angular separation between said first and second optical beams is larger than the absolute value of the angle between the first direction and the reference direction, and larger than the absolute value of the angle between the second direction and the reference direction.

A laser system, comprising:

• a laser outputting a laser beam having a wavelength spectrum;
• a beamsplitter disposed to receive said laser beam and divert a portion of said laser beam;
• and
• a Sagnac interferometer disposed with respect to said beamsplitter to receive said diverted portion of said laser beam to measure the wavelength spectrum thereof.

A laser system, comprising:

• a laser outputting a laser beam having a wavelength;
• a beamsplitter disposed to receive said laser beam and divert a portion of said laser beam;
• and
• a Sagnac interferometer disposed with respect to said beamsplitter to receive said diverted portion of said laser beam to measure the wavelength thereof, wherein said Sagnac interferometer comprises a plurality of gratings.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having a wavelength and split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• a first grating arranged so as to diffract the first beam, said first grating oriented to provide a first incident angle and a first diffraction angle, the first diffraction angle depending on the first incident angle and the wavelength, the first incident angle and the first diffraction angle being displaced to the same side of a line normal to the first grating;
• and
• a second grating arranged so as to diffract the first beam after being diffracted by the first grating, said second diffraction grating oriented to provide a second incident angle and a second diffraction angle such that said second incident angle depends on the first diffraction angle, the second diffraction angle depending on the second incident angle and the wavelength, the second incident angle and the second diffraction angle being displaced to the same side of a line normal to the second grating,
• wherein said first and second gratings are oriented so that a change in wavelength in the first optical beam changes the second diffraction angle, said change in said second diffraction angle including (i) a first contribution caused by the change in wavelength on the diffraction of the first beam by the second grating and (ii) a second contribution caused by a change in the second incident angle resulting from the change in the first diffraction angle, said first contribution reinforcing the second contribution.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having a wavelength and to split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• an odd number of at least three gratings disposed along said first and second paths such that each of said odd number of at least three gratings imparts an amount of angular separation between said first and second beams;
• and
• a beam expander disposed along said first and second paths to match said first and second beams,
• wherein said odd number of at least three gratings are disposed such that said first and second optical beams in said output beam path have a total amount of angular separation that is larger than the angular separation imparted by any one of the odd number of at least three gratings.

A Sagnac interferometer, comprising:

• a beamsplitter arranged to receive an input beam of light having a wavelength and to split said input beam into first and second beams that travel along first and second paths, respectively, said first and second beams recombining along an output beam path;
• and
• an even number of at least four gratings disposed along said first and second paths such that each of said even number of at least four gratings imparts an amount of angular separation between said first and second beams;
• wherein said even number of at least four gratings are disposed such that said first and second optical beams in said output beam path have a total amount of angular separation that is larger than the angular separation imparted by any one of the even number of at least four gratings.