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Progress in ultrafast lasers over the last decade
The last decade has been marked by significant progress in the field of ultrafast lasers, which generate optical pulses in the picosecond and femtosecond range. Specialized laboratory laser systems, in other words, have been transformed into compact, reliable instruments. These laser systems have been dramatically improved and opened up new frontiers for applications by achievements by dint of developments of semiconductor lasers for optical pumping and fast optical saturable absorbers, based on either semiconductor devices or the optical nonlinear Kerr effect.
Market growth and applications
The ultrafast laser market is not just growing, it is accelerating. Ultrafast lasers are able to provide high peak power without thermal damage, which makes them better suited for biomedical and biological applications. The major factor driving the growth of the ultrafast laser market is the rise in demand for ultrafast lasers across biomedical applications. Also, another major factor is increasing the need for cost-efficient solutions for micromachining. The global market for ultrafast lasers is expected to reach nearly $5,5 billion in 2019, registering a compound annual growth rate of 23,7% for the period 2014-2019.
Principles of ultrafast pulsed lasers
The action of ultrafast pulsed lasers is based on such phenomena of ultrafast optics and ultrafast laser physics as like Kerr effect and saturable absorbers. The Kerr effect leads to self-phase modulation. It also allows for Kerr lens mode locking. Related nonlinearities, such as Raman scattering and self-steepening, occur when the nonlinearity has a finite response time. Saturable absorbers, in their turn, used for passive mode locking, introduce optical losses which are reduced for high optical intensities.
Types of ultrafast lasers
The most important types of ultrafast lasers are Ti:Sapphire lasers, diode-pumped lasers, fiber lasers based on rare-earth-doped glass fibers, and mode-locked diode lasers. Several important applications benefit from laser development.
Ultrashort pulse duration
Ultrashort pulse duration. The ultrashort pulse of light is an electromagnetic pulse whose time duration is of the order of a picosecond or less. These pulses have a broadband optical spectrum and can be created by mode-locked oscillators. This special pulse duration allows fast temporal resolution.
High pulse repetition rate
Lasers with multi-gigahertz repetition rates are key components of many applications. They are used in high-capacity telecommunication systems, photonic switching devices, optical interconnections, and the like. High average power 10-2100 GHz sources at shorter wavelengths are promising sources for optical clocks in integrated circuits. Optical clocks can be precisely injected into specific circuits inside a VLSI microprocessor and have the potential to reduce on-chip power requirements, skew, jitter, and scaling to high clock rates beyond 40 GHz.
Broad spectrum
The broad spectrum supports good spatial resolution for optical coherence tomography, a technique for non-invasive cross-sectional imaging in biological systems. Also, the broad spectrum can be useful for stabilizing the electric field underneath the pulse envelope, which is important in highly nonlinear processes such as photoionization and high-harmonic generation.
High peak intensity
The high peak intensity of the pulse can be used to alter materials by “cold” ablation (when a material is changed to gas directly from a solid) or to generate other colours/wavelengths through nonlinear frequency conversion.
Ultrafast lasers have been developing for three decades and are expected to develop further in the future. The main features that are expected to improve are pulse frequency, power levels, and manufacturing costs.