Optics for the Near Infra-Red

Wavelength range: 700 – 3000nm

The near infra-red region of the electromagnetic spectrum (for our purposes covering a wavelength range of 700 nanometers to 3 microns) lies just beyond the sensitivity of the eye. It is a spectral region of immense importance in which many advances in technology are occurring. The entire field of optical communications depends on two narrow spectral bands centered at 1310 nm and 1550 nm. At these wavelengths, optical fibers exhibit both a high transmission and a relatively low dispersion making optical communication over long distances possible. Ultra-fast phenomena are studied using broad tunable laser sources at wavelengths in the 800 – 1200 nm range. The Nd: YAG laser, with its fundamental at 1064 nm, has become an industrial workhorse for laser machining of materials as well as many other applications. Further out into the near IR some important surgical procedures utilize wavelengths in the 2-3 µm range.

Sources of near infra-red radiation included GaAs, AlGaAs and InGaAsP diode lasers, Ti: Sapphire lasers, Nd: YAG and Nd: YLF lasers, Tm: Ho: YAG and Er: HF lasers as well as a number of broadband sources.

Materials for use in infra-red optics are much the same as those used throughout the visible range. Almost all the optical materials transmit well into this region and their optical properties continue to behave in a predictable manner. Coatings are also similar and utilize the same deposition verification of performance is no longer possible and instrumental techniques have to be used. Many of the optics for use in this region are small. This is particularly true of optics for telecommunications where it is necessary to build optical processors into a compact space. This requires microscopic handling and assembly procedures under clean room conditions. The whole field of micro-optics has been developed to meet this need.

Lambda is actively involved in the supply of large quantities of micro-optics to telecom equipment manufacturers and is fully familiar with techniques for the manufacture of these small parts. Special coating and dicing techniques have been developed at Lambda to meet these demands.