Some Important Properties of Femtosecond Lasers
Femtosecond lasers are lasers that can emit optical pulses with a duration of less than 1 ps (ultrashort pulses), that is, in the femtosecond time domain (1 fs = 10−15 s). Therefore, such lasers are also classified as ultrafast lasers or ultrashort pulse lasers. For generating such short pulses, a technique called passive mode locking is often used.
1. Pulse duration (adjustable within a certain range under certain circumstances)
2. Pulse repetition rate (fixed in most cases, or adjustable only within a small range)
Average output power and pulse energy
There are other very important aspects:
The Time Bandwidth Product (TBP) characterizes whether the spectral bandwidth is greater than the desired bandwidth for a given pulse duration. Pulse quality includes additional aspects, such as details of the pulse shape in time and frequency, as well as temporal or spectral side lobes.
Some femtosecond lasers provide a stable linearly polarized output, while others emit indeterminate states of polarization.
Different types and modes of femtosecond lasers have very different noise characteristics. This includes the timing of noise pulses (timing jitter), pulse energy (intensity noise), and various types of phase noise. Stability of the detected pulse parameters is also important, including sensitivity to external influences such as mechanical vibration or optical feedback.
Some lasers have built-in pulse repetition rate stabilization settings for an external reference, or for tuning the output wavelength.
The laser output can be delivered into free space, such as through the glass windows of a house, or through a fiber optic connector.
Built-in features to monitor output power, wavelength and pulse duration can be handy.
Other potential features, such as housing size, power consumption, cooling needs, interface synchronization or computer control.