How does saturable absorber work?
A saturable absorber is an optical component with a certain absorption loss for light, which is reduced at high optical intensities. Such nonlinear absorption can occur, e.g., in a medium with absorbing dopant ions, when a strong optical intensity leads to depletion of the ground state of these ions.
What is passive mode locking?
Passive mode-locking techniques are those that do not require a signal external to the laser (such as the driving signal of a modulator) to produce pulses. Rather, they use the light in the cavity to cause a change in some intracavity element, which will then itself produce a change in the intracavity light.
What is a saturable process?
Drug absorption is the process by which a drug molecule moves from the site of administration to the systemic circulation. Following intravenous administration, there is no absorption process since the drug is directly introduced into the blood stream. This is called saturable drug absorption.
Is achieved by using saturable absorber?
The pulse-formation process is quite complex in passively mode-locked lasers [27]. Fluctuations induced by spontaneous emission are enhanced by the saturable absorber during multiple round trips inside the laser cavity until an intense pulse capable of saturating the absorber is formed.
What is active and passive mode locking?
Passive Mode Locking In a passively mode-locked laser, the loss modulation is done by a saturable absorber, such as a SESAM. This mechanism allows us to generate shorter pulses than with active mode locking. The reason is that the shorter the circulating pulses become, the faster the loss modulation.
What is meant by Q switching?
Q-switching, sometimes known as giant pulse formation or Q-spoiling, is a technique by which a laser can be made to produce a pulsed output beam. Hellwarth and F.J. McClung at Hughes Research Laboratories using electrically switched Kerr cell shutters in a ruby laser.
What is saturable transporter?
Saturable transport systems have the advantage of being responsive to physiological and pathological stimuli. Since saturable systems can regulate peptide entry into the brain, they have the potential to play controlling roles in feeding behavior.
What is saturation in optics?
The saturation power of a laser gain medium is the optical power of an input signal which in the steady state leads to a reduction in the gain to half of its small-signal value. The quantity σabs is zero for four-level gain media but should not be forgotten for quasi-three-level gain media.
What is gain saturation in laser?
Gain saturation is the primary mechanism that determines the power level at which a laser will oscillate. When a laser oscillator begins to oscillate, the oscillation amplitude grows first until the intensity inside the cavity is sufficient to saturate down the laser gain.
How does a saturable absorber mirror ( Sam ) work?
The SAM is a nonlinear mirror. The reflectance increases with increasing pulse energy. Using a saturable absorber mirror (SAM), a self-starting, passively mode-locked diode pumped laser with a very stable pulse repetition rate can be realized.
What are the parameters of a saturable absorber?
A saturable absorber is a material that has decreasing light absorption with increasing light intensity. The key parameters for a saturable absorber are its wavelength range (where it absorbs), its dynamic response (how fast. Fig. 1. History of mode-locked pulsed laser technology [2].
How are saturable absorbers used in mode locked lasers?
In some mode-locked diode lasers, a saturable absorber section is created simply by not pumping that region. A faster recovery can be obtained by implanting nitrogen (N +) ions. For passive Q switching of solid-state lasers in the 1-μm spectral region, Cr 4+ :YAG saturable absorber crystals are most popular [15, 11].
What are the requirements for a saturable absorber for a Q switching laser?
Typical requirements on a saturable absorber for a passively Q-switched laser are: The total non-saturated absorption must be relatively high – often slightly smaller than the small-signal gain of the laser medium, if a high pulse energy and short pulse duration is desired.