Technical Notes

PCFs are generally divided into two main categories: Index Guiding Fibers that have a solid core, and Photonic Bandgap Fibers that have periodic microstructured elements and a core of low index material (e.g. hollow core).

This technical note discusses the fundamental physics of optical fibers, their practical implementation, and the various types of optical fibers.

This Tech Note will be able to help you distinguish which type of fiber you have or require, which connector your fiber has or will need, and how to terminate a fiber connector.

A fused coupler basically consists of two, parallel optical fibers that have been twisted, stretched and fused together so that their cores are very close to each other. This forms a Coupling Region as shown.

Choosing a coupling optic for a multi-mode fiber is relatively simple. Select an optic whose numerical aperture (NA) is closest to matching that of the fiber.

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.

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.

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.

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.

In addition to being deposited on the surface of an optical component, optical coatings can also be incorporated into a single element through deposition on one or many substrates followed by a lamination process.

Optical coatings typically consist of thin films made up of single or multiple layers of either metallic or dielectric materials. When properly designed and fabricated, these coatings can dramatically modify the reflection and transmission properties of an optical component.

Lenses are essentially light-controlling elements and so are exploited for light gathering and image formation.

Optical mirrors consist of metallic or dielectric films deposited directly on a substrate such as glass, differing from common mirrors, which are coated on the back surface of the glass.

A diffraction grating is essentially a multi-slit surface. It provides angular dispersion, i.e., the ability to separate wavelengths based on the angle that they emerge from the grating.

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.

Polarization-dependent loss (PDL) is an important characteristic of optical components used in telecommunications networks. This Technical Note provides the precise definition that Richardson Gratings uses for the PDL of its gratings, and explains the measurement procedure used to determine PDL values.

This Technical Note examines the causes of unwanted light from gratings and in spectrometers and describes how these forms of unwanted light are measured. The terminology of SRE is not standard, so for clarity we refer to unwanted light from the surface of the grating itself as scattered light, and unwanted light reaching the detector of a grating-based instrument as stray light.

A diffraction grating is a first surface optic, so its surface cannot be touched or otherwise come in contact with another object without damaging it and perhaps affecting its performance. Damage can take the form of contamination (as in the adherence of finger oils) or distortion of the microscopic groove profile in the region of contact. This Technical Note describes the reasons why a grating must be handled carefully and provides guidelines for doing so.

The problem of coupling light into an optical fiber is really two separate problems. In one case, we have the problem of coupling into multimode fibers, where the ray optics of the previous section can be used. In the other case, coupling into single-mode fibers, we have a fundamentally different problem. In this case, one must consider the problem of matching the mode of the incident laser light into the mode of the fiber.

Beam expansion or reduction is a common application requirement in most labs using lasers or light sources and optics. There are many ready-made beam expanders available on the market, but often they are not available in the required expansion ratio or spectral range. And, for students or those working within a tight budget, the plug and play solution may not be the answer.