A Distributed Feedback Laser comprises a layer stack comprising a p-layer, an n-layer which are arranged so as to form an pn-junction having an active layer in between. Within the layer stack, an index coupled grating layer or a grating layer is arranged which comprises a first, a second, and a third grating portion. The first, the second, and the third grating portions are asymmetrically arranged along a lateral dimension of the layer stack, wherein the second grating portion is formed without a grating structure.

A VCSEL can include: an elliptical oxide aperture in an oxidized region that is located between an active region and an emission surface, the elliptical aperture having a short radius and a long radius with a radius ratio (short radius)/(long radius) being between 0.6 and 0.8, the VCSEL having a relative intensity noise (RIN) of less than ?140 dB/Hz. The VCSEL can include an elliptical emission aperture having the same dimensions of the elliptical oxide aperture. The VCSEL can include an elliptical contact having an elliptical contact aperture therein, the elliptical contact being around the elliptical emission aperture. The elliptical contact can be C-shaped. The VCSEL can include one or more trenches lateral of the oxidized region, the one or more trenches forming an elliptical shape, wherein the oxidized region has an elliptical shape. The one or more trenches can be trapezoidal shaped trenches.

A wavelength estimation device including a light detector to receive light emitted from a light source and an estimation unit. The estimation unit estimates a wavelength of the light based on an amount of light received by the light detector.

A surface-emitting laser includes a resonator and an electrode pair connected to a power supply, through which a current is injected into an active layer. The resonator includes the active layer to oscillate a laser beam; a first reflector; and a second reflector facing the first reflector with the active layer therebetween. The resonator has an optical thickness 1.5 times or more than a wavelength of the laser beam in a vacuum. The surface-emitting laser does not oscillate the laser beam during a current injection period in which the power supply injects the current into the active layer through the electrode pair; and oscillates and emits the laser beam during a current decrease period after the current injection period. The current injected into the active layer during the current decrease period is lower than the current injected into the active layer during the current injection period.

A laser drive circuit compensates for laser diode dynamics. A compensation value is determined from a sum of weighted basis functions. The basis functions may be a function of current desired optical powers and/or past desired optical powers. The weights may be updated periodically based at least in part on accumulated basis function outputs and measured optical powers.

A performance estimation method for estimating performance of a laser device including a chamber and a pair of electrodes arranged in the chamber includes acquiring a target feature including at least one of a gas pressure in the chamber and an application voltage between the electrodes, and a component replacement scenario including a replacement component and a replacement timing; acquiring a trained recurrent neural network model corresponding to the target feature; acquiring past data of the laser device corresponding to the recurrent neural network model; creating data of a number of used pulses of the replacement component in future based on the component replacement scenario; estimating, by the recurrent neural network model, performance of the target feature in the component replacement scenario based on the past data and the data of the number of used pulses of the replacement component in future; and outputting a result of the estimation.

Described herein are examples of improved semiconductor lasers having improved facet reliability for operation at high power and high current without significant change in device performance. The semiconductor laser may include a first semiconductor layer, an active layer, a second semiconductor layer sequentially adjacent to each other and arranged on a substrate, and a contact layer. In one example, the improved semiconductor laser may have a conductive contact less than the length of the semiconductor laser cavity and/or a dielectric layer arranged on at least one of the end portions of the contact layer.

A semiconductor light-emitting element includes: a substrate; an n-type clad layer above the substrate; an active layer above the n-type clad layer; and a p-type clad layer above the active layer. The active layer includes: a well layer; an n-side first barrier layer on an n-type clad layer side of the well layer; and a p-side barrier layer on a p-type clad layer side of the well layer. The p-side barrier layer comprises In. The n-side first barrier layer has an In composition ratio lower than an In composition ratio of the p-side barrier layer. The n-side first barrier layer has a band gap energy smaller than a band gap energy of the p-side barrier layer.