Sample interview questions: What are some common techniques for achieving ultrashort laser pulses in the infrared range?
Sample answer:
1. Kerr-lens mode-locking:
– Uses the intensity-dependent refractive index of a material to create a self-focusing effect, leading to the formation of ultrashort pulses.
– Common materials used include titanium-sapphire and neodymium-doped yttrium aluminum garnet (Nd:YAG).
2. Semiconductor saturable absorber mirrors (SESAMs):
– Utilize the saturable absorption characteristics of semiconductor materials to achieve mode-locking.
– The absorption is reduced for high-intensity pulses, allowing them to pass through the mirror while blocking low-intensity pulses.
3. Active mode-locking:
– Employs an external modulator to modulate the gain or loss of the laser cavity, resulting in the generation of ultrashort pulses.
– Techniques include electro-optic and acousto-optic modulation.
4. Passive harmonic mode-locking:
– Utilizes the nonlinear properties of a material to generate higher harmonics of the fundamental laser frequency.
– These harmonics can then be used to create ultrashort pulses through subsequent nonlinear interactions.
5. Soliton mode-locking:
– Relies on the formation of solitons, which are self-stabilizing pulses that maintain their shape and duration as they propagate through a nonlinear medium.
– Can be achieved through the use of dispersion-managed fiber lasers or other nonlinear systems.
Apart from these techniques, there are several other factors that can influence the gen… Read full answer