High power laser diodes

Fibre lasers, disk lasers and direct diode systems are being used for an ever growing number of applications. These relatively new laser systems are extending their application range, due to their high beam quality, increased brightness, flexible and compact design and scalability.  The efficiency of high laser diode systems, some originally developed for telecoms, is now giving greater cost effectiveness than that afforded by conventional processes or alternative laser devices for a range of sectors, including industrial, medical, printing and automotive.  One of the most important processes in the development of high power laser diode systems is the deposition of optical coatings which are compatible with the high optical intensities found at the laser facets.  Helia have developed a range of high-power facet coatings at a number of wavelengths for this application, for example at 980nm, 808nm, 780nm and other wavelengths.

Blue laser diodes

Over the last decade, there has been a rapid development of gallium nitride based semiconductor laser diodes which emit in the blue and near ultra violet part of the spectrum.  Such diodes have mass use in optical memory read and write, as well as such disparate applications as displays and bio-medicine.  Helia have developed facet coatings tailored for the unique properties of this class of semiconductor laser.

Diffractive optics

Diffractive optical elements are used to manipulate optical beams, particularly from laser sources.  By using the diffractive effects commonly seen from elementary ruled diffracting gratings, more sophisticated two-dimensional diffractive elements are computer-generated to form optical patterning used, for example, to split light into multiple beams or to place pictures within the beam, eg for advertising logos.  In order to improve optical transmission, Helia has a long history of anti-reflection coating a range of sophisticated diffractive optical elements.

Thin film filters

High transition thin film filters (TFFs) with sharp spectral features and high durability, developed for the communications market, are being deployed in an innovative range of end products, such as fluorescence microscopes for DNA sequencing and flow cytometry.  Another emerging market is displays where the next generation of projectors is using LEDs. Their performance is critically dependent on the efficiency of TFFs in the collection and multiplexing – ie the combining of multiple wavelengths of light – of LEDs emitting in the primary colour bands.   

VCSELs

The vertical cavity surface emitting laser (VCSEL) is a semiconductor laser that emits light perpendicular to the semiconductor substrate.   These devices have sophisticated epitaxial growth which form high quality optical microcavities to produce the optical feedback necessary for laser operation.  The vertical cavity geometry permits an excellent circular spatial mode, well suited for integration with optical fibres, as well as a number of other applications.  The high quality cavity also permits a spectrally pure output, which can be use for short haul telecommunications, for example, as well gas monitoring, atomic clocks and various imaging systems.  Helia has many years experience in producing high-reflectivity dielectric top mirrors on VCSELs, and can produce the low-stress coatings compatible with the high optical intensities found in these lasers.