Monolithic optical retarder

A metrology system comprising:

• an illumination source to generate an illumination beam;
• one or more illumination optics to direct the illumination beam to a sample;
• a detector;
• one or more collection optics to collect light from the sample as a collected beam and direct at least a portion of the collected beam to the detector as detected light,
• one or more monolithic optical retarders associated with at least one of the one or more illumination optics or the one or more collection optics, wherein a particular monolithic optical retarder of the one or more monolithic optical retarders comprises:
• a monolithic prism comprising:
• an input face for receiving a light beam;
• an output face aligned with an optical axis of the light beam prior to entering the input face;
• and
• three or more reflection faces, wherein the three or more reflection faces are oriented to provide an optical path for the light beam from the input face to the output face via total internal reflection by the three or more reflection faces, wherein the monolithic optical retarder imparts a selected optical retardation on the light beam upon propagation along the optical path based on total internal reflection on the three or more reflection faces, wherein the input face, the output face, and the three or more reflection faces are oriented to provide that an optical axis of the light beam exiting the output face is equal to the optical axis of the light beam entering the input face, wherein the three or more reflection faces comprise one or more retarding faces, wherein incident angles of the light beam on the one or more retarding faces are greater than a critical angle for total internal reflection, wherein the total optical retardation on the light beam upon propagation along the optical path corresponds to cumulative optical retardations on the light beam imparted by the one or more retarding faces;
• and
• a controller communicatively coupled to the detector, wherein the controller includes one or more processors configured to execute program instructions causing the one or more processors to generate one or more metrology measurements of the sample based on the detected light.

A metrology method comprising:

• generating an illumination beam;
• directing the illumination beam to a sample;
• collecting light from the sample in response to the illumination beam as a collected beam, wherein a polarization of at least the illumination beam or the collected beam is controlled by at least one monolithic optical retarder formed from a monolithic prism comprising:
• an input face for receiving a light beam;
• an output face aligned with an optical axis of the light beam prior to entering the input face;
• and
• three or more reflection faces, wherein the three or more reflection faces are oriented to provide an optical path for the light beam from the input face to the output face via reflection by the three or more reflection faces, wherein the monolithic optical retarder imparts a selected optical retardation on the light beam upon propagation along the optical path based on total internal reflection on at least one of the three or more reflection faces, wherein the input face, the output face, and the three or more reflection faces are oriented to provide that an optical axis of the light beam exiting the output face is equal to the optical axis of the light beam entering the input face, wherein the three or more reflection faces comprise one or more retarding faces, wherein incident angles of the light beam on the one or more retarding faces are greater than a critical angle for total internal reflection, wherein the total optical retardation on the light beam upon propagation along the optical path corresponds to cumulative optical retardations on the light beam imparted by the one or more retarding faces;
• directing at least a portion of the collected beam to a detector as detected light;
• and
• generating one or more metrology measurements of the sample based on the detected light.

A monolithic optical retarder comprising:

• a monolithic prism comprising:
• an input face for receiving a light beam;
• an output face aligned with an optical axis of the light beam prior to entering the input face;
• and
• three or more reflection faces, wherein the three or more reflection faces are oriented to provide an optical path for the light beam from the input face to the output face via reflection by the three or more reflection faces, wherein the monolithic optical retarder imparts a total optical retardation on the light beam upon propagation along the optical path based on total internal reflection on at least one of the three or more reflection faces, wherein the input face, the output face, and the three or more reflection faces are oriented to provide that an optical axis of the light beam exiting the output face is aligned with the optical axis of the light beam entering the input face, wherein the three or more reflection faces include one or more non-retarding faces, wherein incident angles of the light beam on the one or more non-retarding faces are lower than a critical angle for total internal reflection, wherein the one or more non-retarding faces impart zero optical retardation on the light beam.

A metrology system comprising:

• an illumination source to generate an illumination beam;
• one or more illumination optics to direct the illumination beam to a sample;
• a detector;
• one or more collection optics to collect light from the sample as a collected beam and direct at least a portion of the collected beam to the detector as detected light,
• one or more monolithic optical retarders associated with at least one of the one or more illumination optics or the one or more collection optics, wherein a particular monolithic optical retarder of the one or more monolithic optical retarders comprises:
• a monolithic prism comprising:
• an input face for receiving a light beam;
• an output face aligned with an optical axis of the light beam prior to entering the input face;
• and
• three or more reflection faces, wherein the three or more reflection faces are oriented to provide an optical path for the light beam from the input face to the output face via total internal reflection by the three or more reflection faces, wherein the monolithic optical retarder imparts a selected optical retardation on the light beam upon propagation along the optical path based on total internal reflection on the three or more reflection faces, wherein the input face, the output face, and the three or more reflection faces are oriented to provide that an optical axis of the light beam exiting the output face is equal to the optical axis of the light beam entering the input face, wherein the three or more reflection faces include one or more non-retarding faces, wherein incident angles of the light beam on the one or more non-retarding faces are lower than a critical angle for total internal reflection, wherein the one or more non-retarding faces impart zero optical retardation on the light beam;
• and
• a controller communicatively coupled to the detector, wherein the controller includes one or more processors configured to execute program instructions causing the one or more processors to generate one or more metrology measurements of the sample based on the detected light.

A metrology method comprising:

• generating an illumination beam;
• directing the illumination beam to a sample;
• collecting light from the sample in response to the illumination beam as a collected beam, wherein a polarization of at least the illumination beam or the collected beam is controlled by at least one monolithic optical retarder formed from a monolithic prism comprising:
• an input face for receiving a light beam;
• an output face aligned with an optical axis of the light beam prior to entering the input face;
• and
• three or more reflection faces, wherein the three or more reflection faces are oriented to provide an optical path for the light beam from the input face to the output face via reflection by the three or more reflection faces, wherein the monolithic optical retarder imparts a selected optical retardation on the light beam upon propagation along the optical path based on total internal reflection on at least one of the three or more reflection faces, wherein the input face, the output face, and the three or more reflection faces are oriented to provide that an optical axis of the light beam exiting the output face is equal to the optical axis of the light beam entering the input face, wherein the three or more reflection faces include one or more non-retarding faces, wherein incident angles of the light beam on the one or more non-retarding faces are lower than a critical angle for total internal reflection, wherein the one or more non-retarding faces impart zero optical retardation on the light beam;
• directing at least a portion of the collected beam to a detector as detected light;
• and
• generating one or more metrology measurements of the sample based on the detected light.