Amplified Spontaneous Emission Source (ASE) ASE sources have very low coherence, corresponding to the large emission bandwidth. They contain a laser gain medium that is excited to emit and then amplify luminescent light. They are alternatively known as superluminescent sources. Their properties make them useful in applications such as fluorescence excitation, and spectroscopy. DPSS Laser Diode-pumped solid state (DPSS) lasers use laser diodes rather than flash or arc lamps for optically pumping solid-state laser cavities. Although lamps are low cost and can provide high powers, they also give lower lifetimes, low power efficiencies and introduce unwanted thermal effects.
In comparison, DPSS lasers have a compact footprint and deliver efficient power consumption. They also offer potentially long lifetimes, low noise and high beam quality. Excimer Laser An excimer laser uses a gas mixture as the gain medium. This is typically a combination of a noble gas and a reactive gas. Pumped with a high voltage electric discharge in short pulses, the gases create excimers, pseudo molecules that only exist in an energized state. These usually emit laser light in the UV region.
External Cavity Diode Laser External cavity diode lasers combine a laser diode with external optics that extend the resonant cavity beyond the laser diode. By extending the cavity, the laser linewidth is narrowed, phase noise is reduced and the wavelength can be adjusted. Fibre Laser A fibre laser is a solid-state laser and is based around an optically pumped doped optical fibre. As the gain media has a large gain bandwidth, wide wavelength tuning ranges and ultrashort pulses are achievable. The high gain efficiency allows operation with small pump powers, giving high power efficiencies and contributes to their small size and power consumption. Their high output power, without amplifiers, eliminates spontaneously induced noise. This is particularly useful in sensing applications. Furthermore, the potential for long cavity length produces very narrow linewidth and high coherence with low phase noise. This is particularly useful for high-resolution interferometry. Single mode fibres give diffraction limited beam quality making them ideally suited to high performance material processing applications.
High output power and compact size are the trademarks of fibre lasers. As fibre laser construction is inherently more robust than other laser types, it lends itself to industrial and portable applications. Gas Laser These lasers use an electrically pumped gas mixture as the gain medium. Examples include lasers such as Helium-Neon, Argon Ion, Krypton ion that deliver outputs in the visible; Carbon Dioxide delivers outputs in the Infrared; and Nitrogen and a range of Excimer lasers output in the UV. Gas lasers have largely been replaced by the newer diode, DPSS and fibre laser technologies. However, they are still the only solution for very specific wavelengths. Laser Diode A laser diode uses electrically pumped semiconductor gain medium. Laser diodes are highly sensitive light sources.
The Laser 2000 range of laser diode current controllers, laser diode temperature controllers and laser diode mounts allow the output power, wavelength and mode stability to be adjusted with high precision, resolution and stability. This enables sensitive control and measurement. LED Light Emitting Diode A light emitting diode is a semiconductor device that emits light through electroluminescence. LEDs emit low powers in the UV, visible and infrared parts of the spectrum. They are broadband sources that are suitable for applications such as illumination, fluorescence excitation, sensing and spectroscopy. They are also used in low data rate optical communications. Quantum Cascade Laser / External Cavity Quantum Cascade Laser A Quantum Cascade Laser (QCL) is a semiconductor laser that emits highly coherent radiation in the mid- to long-wave infrared region of the spectrum.
QCLs are not diode lasers, but rather unipolar semiconductor devices consisting of hundreds of epitaxial grown layers forming a large number of quantum wells in the conduction band of the device. These are engineered to enable a cascade of photons emitted for each injected electron. QCLs generate light in the 4µm to 25µm region of the electromagnetic spectrum.
An External Cavity Quantum Cascade Laser (ECqcL™) is a semiconductor laser source. It integrates quantum cascade gain media into an external cavity having wavelength dependent feedback. ECqcLs™ are available either as precision fixed-wavelength sources, or as broadly tunable lasers. A tunable ECqcL™ can tune across the entire gain profile of the QC chip, allowing for tunability of 10% to 25% of the center wavelength. Solid State Laser Solid state lasers are based around a solid gain media such as ion-doped crystals or glasses, (e.g. Nd:YAG, Nd:YLF, Ti:sapphire, Nd:YVO4 etc...). These lasers have the ability to deliver highly coherent radiation in the UV, visible or Infrared ranges of the spectrum, in pulsed or CW forms and with high optical output power and quality. They also offer the ability to operate in highly singlemode states for applications requiring long and stable coherence. High powers can also be achieved, making them suitable for some materials processing applications.
Superluminescent Light Emitting Diode (SLED) SLEDs are semiconductor devices that incorporate high-power gain sections to give amplified spontaneous emission. Similar in construction to laser diodes, but without optical feedback to cause laser action, they combine the high power and brightness of laser diodes with the low coherence of conventional light-emitting diodes.