Local oscillator tap using reflection for coherent lidar

A method of operating a lidar device, the method comprising:

• emitting, via a laser source, a transmit beam;
• transmitting, via an optical scanner comprising at least one lens, a first portion of the transmit beam towards a target;
• receiving, via the optical scanner, a receive beam reflected by the target;
• reflecting a second portion of the transmit beam at a media-air interface defined at an end of a transmission medium where the first portion of the transmit beam is launched into air towards the at least one lens of the optical scanner, the transmission medium being configured to provide a propagation path for the transmit beam and the receive beam;
• and
• determining, via a target detection module, a range and/or a velocity of the target based on the receive beam and the second portion of the transmit beam, wherein the media-air interface comprises a grating integrated within the transmission medium.

A method of manufacturing a lidar device, the method comprising:

• optically coupling (i) a laser source configured to emit a transmit beam, (ii) an optical scanner, comprising at least one lens, configured to transmit a first portion of the transmit beam towards a target and receive a receive beam reflected by the target, and (iii) a transmission medium configured to provide a propagation path for the transmit beam and the receive beam;
• adjusting a configuration of a media-air interface defined at an end of the transmission medium where the first portion of the transmit beam is launched into air towards the at least one lens of the optical scanner to control at least one characteristic of a second portion of the transmit beam reflected at the media-air interface, wherein the media-air interface comprises a grating integrated within the transmission medium;
• and
• configuring a target detection module to determine a range and/or a velocity of the target based on the receive beam and the second portion of the transmit beam.