Technical Notes

Spatial filters provide a convenient way to remove random fluctuations from the intensity profile of a laser beam. This greatly improves resolution — which is especially critical for applications like holography and optical data processing.

Learn about laser classifications and the controls and protective equipment required to stay safe.

To assess the quality, performance, and characteristics of laser diodes, manufacturers often perform exhaustive testing which requires electro-optical, spectral and spatial characterization of the laser output.

Thermopile sensors are based on thermocouples. A thermocouple consists of two dissimilar metals connected in series. To detect radiation, one metal junction is typically blackened to absorb the radiation.

A pyroelectric crystalline material has electric polarization even in the absence of an applied voltage. On heating, the material expands and produces a change in the polarization which builds up a charge on the opposite surface.

A photodiode sensor consists of a semiconductor p-n junction. Light falling on the junction causes the formation of electron-hole pairs. In photovoltaic mode, the electron-hole pairs migrate to opposite sides of the junction, producing a voltage.

Precise control of polarization behavior is necessary to obtain optimal performance from optical components and systems. Characteristics such as reflectivity, insertion loss, and beamsplitter ratios will be different for different polarizations.

When equipped with high-performance thermal imaging systems, UAVs, also known as drones, lend themselves to a wide range of defense, government, and commercial applications.

A laser is a source of coherent light. It contains an optical oscillator that increases the amplitude of an optical field while maintaining its phase. This coherent amplification is achieved through Light Amplification by Stimulated Emission of Radiation (LASER).

Light is generated from a laser as a result of the following process: electrons in a material move from an excited energy level to a lower-lying energy level and produce photons that contribute to the laser beam.

Simple beam expanders are essentially telescopes which, in their most basic forms, consist of two lenses. The input beam is assumed to be collimated. The first lens must have a diameter larger than the diameter of the input beam to avoid clipping the beam.

Variable laser attenuators consist of essentially two optical components, a half waveplate, and a polarizer with a good extinction ratio, and allow for continuous power control for linearly polarized lasers.

Measurement techniques of the power, flux (equivalent to power but measured in units of lumens), and spectrum of LEDs is not very different from that of traditional light sources.

The irradiance distribution of a laser beam is determined by the transverse modes that exit the laser cavity. Typically, the lowest-order transverse mode (TEM00) is selected for emission since it propagates with the least beam divergence and can be focused to the tightest spot.

The most common laser light characteristics include: wavelength, gain bandwidth, monochromaticity, spatial and temporal profiles, collimation, output power, coherence and polarization.

The critical components of a laser are a gain medium (acts as medium for population inversion), a pump source (serves as energy source for inverting population), and a resonator (provides feedback).

Lasers are typically identified by their gain medium and are often classified by the radiating species that give rise to stimulated emission. These radiating species can include atoms and molecules in a dilute gas, organic molecules dissolved at relatively low concentration in liquid solutions, semiconductor materials, and dielectrics such as crystalline solids or glasses that are doped with a high concentration of ions.

It is often desirable to operate lasers in a pulsed mode since this can significantly increase the peak output power.

The first way to perform laser wavelength tuning uses a wavelength-selective element to choose a specific portion under a gain bandwidth to lase. The second method of wavelength tuning involves nonlinear frequency conversion.

Laser diodes possess several unique attributes compared to other types of lasers. They are very small compared to other classes of lasers, can operate very efficiently with relatively low input powers, and are compatible with modern electronics.