How does mode-locked laser work?

Mode locking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds (10−12 s) or femtoseconds (10−15 s). The basis of the technique is to induce a fixed phase relationship between the longitudinal modes of the laser’s resonant cavity.

How do you frequency lock a laser?

The simplest and most straightforward approach is to lock to the side of the cavity transmission fringe. The side-fringe locking technique uses the slope on either side of the transmission peak to convert frequency fluctuations of the laser into amplitude fluctuations, which are subsequently detected by a photodiode.

What is a laser frequency comb?

Optical frequency combs are specialized lasers that act like a ruler for light. They measure exact frequencies of light — from the invisible infrared and ultraviolet to visible red, yellow, green and blue light — quickly and accurately. These Nobel Prize-winning devices fill an important technological gap.

What is phase locking laser?

Optical phase-locking is a common technique for transferring the frequency and phase characteristics of one laser beam to another. It is commonly used in heterodyne metrology, free-space optical communications and spectroscopic applications.

What is the advantage of mode locking?

Advantages of fundamental mode locking are that possible instabilities of harmonic mode locking are avoided, and that the laser setup is usually more compact. On the other hand, harmonically mode-locked lasers have a potential for lower laser noise.

What is laser frequency stabilization?

High frequency-stabilized, narrow-linewidth lasers have been constructed by PDH technique to lock the laser frequencies to the resonance of reference cavities. The frequency stability of a laser which is locked to a reference cavity is dominated by the effective length stability of the reference cavity.

What is frequency stabilization?

[′frē·kwən·sē ‚stā·bə·lə′zā·shən] (communications) Process of controlling the center or carrier frequency so that it differs from that of a reference source by not more than a prescribed amount.

How is frequency comb generated?

The most popular way of generating a frequency comb is with a mode-locked laser. Such lasers produce a series of optical pulses separated in time by the round-trip time of the laser cavity. This series of sharp spectral lines is called a frequency comb or a frequency Dirac comb.

What is difference between Q switching and mode locking?

The Q-switched lasers can generate the output pulses with high energy and short pulse width. On the other hand, the mode-locking process could be achieved by locking the relatives’ phases of oscillating photons inside the cavity (Zaitsu and Tsuchiya, 2018).