In: Electrical Engineering
Describe briefly how the laser is modulated? Using the simple rate equation for carrier and photon density, explain why the high-speed small-signal response will behavior like L-C circuit? Why the bandwidth (resonant frequency) increases as the current increases?
An optical modulator is a device which is used to modulate a beam of light. The beam may be carried over free space, or propagated through an optical waveguide (optical fibre). Depending on the parameter of a light beam which is manipulated, modulators may be categorized into amplitude modulators, phase modulators, polarization modulators etc. Often the easiest way to obtain modulation of intensity of a light beam, is to modulate the current driving the light source, e.g. a laser diode. This sort of modulation is called direct modulation, as opposed to the external modulation performed by a light modulator. For this reason light modulators are, e.g. infiber optic communications, called external light modulators.
With laser diodes where narrow linewidth is required, direct modulation is avoided due to a high bandwidth "chirping" effect when applying and removing the current to the laser.
Please go through the following link
https://googleweblight.com/i?u=https://www.researchgate.net/publication/223141631_High-Speed_Semiconductor_Laser_Design_and_Performance&hl=en-IN