A method to tune an emission wavelength of a wavelength tunable laser apparatus is disclosed. The laser apparatus implements, in addition to a wavelength tunable laser diode (t-LD) integrating with a semiconductor optical amplifier (SOA), a wavelength monitor including an etalon filter. The current emission wavelength is determined by a ratio of the magnitude of a filtered beam passing the etalon filter to a raw beam not passing the etalon filter. The method first sets the SOA in an absorbing mode to sense stray component disturbing the wavelength monitor, then correct the ratio of the beams by subtracting the contribution from the stray component.

A laser comprising a narrow linewidth, comprising: a grating along a laser cavity; a laser waveguide having a plurality of waveguide sections corresponding to a plurality of grating sections, each of the plurality of waveguide sections having a ridge/mesa width for detuning the grating in each of the plurality of grating sections; and a plurality of contact electrodes contacting each of the plurality of waveguide sections, the plurality of contact electrodes for applying a different current to each of the plurality of waveguide sections to enable active feedback noise suppression.

In embodiments, a system for scanning an intraoral cavity comprises an intraoral scanner to generate intraoral scan data of the intraoral cavity and viewfinder images of the intraoral cavity, a display, and a processing unit operatively connected to the intraoral scanner and to the display. The processing unit is to: receive the intraoral scan data and the viewfinder images from the intraoral scanner; generate a three-dimensional (3D) digital model of the intraoral cavity using the intraoral scan data; output the 3D digital model to the display; output the viewfinder images to the display; determine which portions of the intraoral cavity have been scanned; determine a current field of view of the intraoral scanner; determine a visual indicator that provides guidance for positioning and orienting the field of view of the intraoral scanner; and output the visual indicator to the display.

A system for intraoral scanning includes a display, a processing unit, and a scanner to generate scan data and viewfinder images of an intraoral cavity. The processing unit is to: receive the scan data and the viewfinder images; generate a 3D model of the intraoral cavity using the intraoral scan data; output the 3D model to the display; output the viewfinder images to the display; determine which portions of the intraoral cavity have been scanned; determine a current field of view of the scanner; determine, based on the current field of view and the determined portions of the intraoral cavity that have been scanned, a visual indicator that provides guidance for positioning and orienting the field of view of the scanner; and output the visual indicator to the display.

An optical frequency control device includes: a detection circuit to receive first light including a first frequency, receive second light including a second frequency, modulate the first light with a local oscillation signal, and detect a differential beat signal between the frequency of sideband light included in the modulated first light and the second frequency; a light source control circuit to change the second frequency by frequency-dividing the differential beat signal with a first frequency division number, by frequency-dividing a reference signal with a second frequency division number, and by outputting a phase error signal indicating a phase difference between the frequency-divided differential beat signal and the frequency-divided reference signal; and a signal processing unit to set each of the first frequency division number and the second frequency division number according to the set value of a frequency difference between the first frequency and the second frequency.

A laser for a distributed fiber sensing system may have a frequency discriminator integrated with the laser. The laser may be an external cavity laser, with at least a portion of the laser cavity on a planar lightwave circuit, which also includes the frequency discriminator.

Methods, circuits, and techniques for reflection cancellation. Laser output is tapped. A tapped portion of the laser output is phase shifted to generate a feedback signal, with the feedback signal being out-of-phase with a parasitic reflection of the laser output. The feedback signal is directed towards the laser such that the parasitic reflection and feedback signal are superpositioned before entering the laser. A magnitude and a phase of the feedback signal are such that superposition of the feedback signal and the parasitic reflection results in a resulting signal of lower magnitude than the parasitic reflection alone. During laser operation, a magnitude of the resulting signal is monitored and, as the parasitic reflection varies, the magnitude of the resulting signal is adjusted by adjusting at least one of the magnitude and the phase of the feedback signal in response to the monitoring of the resulting signal.

A driver circuit includes a fly capacitor with a first end and a second end. The driver circuit includes a laser diode having an anode and a cathode. The driver circuit is configured to operate in first and second operating states. The anode is coupled to the first end of the fly capacitor. In the first operating state, the cathode is coupled to a first voltage supply node, the first end of the fly capacitor is coupled to a second voltage supply node, and the second end of the fly capacitor is coupled to a first reference terminal. In the second operating state, the cathode is coupled to a second reference terminal and decoupled from the first voltage supply node, the first end of the fly capacitor is decoupled from the second voltage supply node, and the second end of the fly capacitor is coupled to a third reference terminal.

In embodiments, a system for scanning an intraoral cavity comprises an intraoral scanner to generate intraoral scan data of the intraoral cavity and viewfinder images of the intraoral cavity, a display, and a processing unit operatively connected to the intraoral scanner and to the display. The processing unit is to: receive the intraoral scan data and the viewfinder images from the intraoral scanner; generate a three-dimensional (3D) digital model of the intraoral cavity using the intraoral scan data; output the 3D digital model to the display; output the viewfinder images to the display; determine which portions of the intraoral cavity have been scanned; determine a current field of view of the intraoral scanner; determine a visual indicator that provides guidance for positioning and orienting the field of view of the intraoral scanner; and output the visual indicator to the display.

A laser diode drive system for generating a drive current for a laser diode is described. The laser diode drive system comprises a first laser diode driver connected to the laser diode by a first cable to provide a drive current source for the laser diode. A second laser diode driver is then connected to the laser diode by a second cable to provide a low current sink for the laser diode. A feedback control loop is employed to provide a feedback signal for the second laser diode driver from to sample of an output field of the laser diode. The laser diode drive system exhibits low power consumption while being capable of creating sufficient feedback bandwidth to reduce the excess optical noise by at least an order of magnitude at 1 MHz compared with laser diode drive systems comprising just a first laser diode driver.