How do you mode lock a laser?

How do you mode lock a laser?

In an actively mode-locked laser, as shown below, mode locking is achieved with a modulator (for example, electro-optic type), which modulates the resonator losses in exact synchronism with the resonator round-trips. The modulator is often placed near an end of the resonator.

What is mode-locked fiber laser?

A technique for raising the possible pulse energy and/or for lowering the pulse duration of a mode-locked fiber laser is used in stretched-pulse fiber lasers [5, 8, 9, 13, 19, 22], also sometimes called dispersion-managed fiber lasers.

How do mode-locked lasers 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.

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 the difference between Q-switching and mode locking?

Dear Xinyang, passive Q-switching takes place in both cases as in time of “giant” pulse generation so in time of mode locking. Mode locking needs the saturated absorber with relaxation time less then round trip time in the given cavity while the giant pulse generation develops better with slow relaxing absorber.

What is difference between Q switching and mode locking?

What is difference between Q-switching and mode locking?

Why Q-switching is needed in some laser?

Initially the laser medium is pumped while the Q-switch is set to prevent feedback of light into the gain medium (producing an optical resonator with low Q). The net result is a short pulse of light output from the laser, known as a giant pulse, which may have a very high peak intensity.

How does a 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 the femtosecond used for?

The femtosecond laser is a high-energy optics technology used for eye surgeries and other medical procedures, including all-laser LASIK. During this bladeless procedure, your surgeon uses the femtosecond laser to create a flap in your cornea before altering the shape of the underlying tissue to correct your vision.

What is a mode-locked laser?

A mode-locked laser is a laser to which the technique of active or passive mode locking is applied, so that a periodic train of ultrashort pulses is emitted. See the article on mode locking for more details on mode-locking techniques; the present article focuses more on the lasers themselves.

What can RP photonics do for You?

Ask RP Photonics for advice on any aspect of mode locking, e.g. on different mode-locking techniques, types or designs of mode-locked lasers, etc. Dr. Paschotta is a leading expert concerning mode-locked lasers. Also, RP Photonics has powerful numerical software for designing and optimizing mode-locked lasers.

Why do laser resonators need harmonic mode locking?

Fiber laser resonators are usually too long to achieve such repetition rates with fundamental mode locking, i.e. with a single pulse circulating in the resonator. Therefore, harmonic mode locking is often required, where multiple (sometimes hundreds or even thousands) of pulses circulate with a well-defined spacing.

What are the limitations of mode-locked diode lasers?

Although mode-locked diode lasers can be very compact and robust devices, which fit particularly well into optical fiber communications systems, they are subject to various limitations, which do not allow them to reach the full performance potential of, e.g., mode-locked fiber lasers: The pulse energy is fairly limited – often far below 1 pJ.