What is laser modulation technology
Light is a kind of electromagnetic wave with a higher frequency. It has excellent coherence and thus, like previous electromagnetic waves (such as radios and televisions), can be used as a carrier for transmitting information. The information “carried” by the laser (including language, text, images, symbols, etc.) is sent to the receiver through certain transmission channels (atmosphere, optical fibers, etc.), and then identified and restored to the original information by the optical receiver. The process of loading information onto a laser is called modulation, and the device that accomplishes this process is called a modulator. Among them, the laser is called the carrier wave; The low-frequency information that plays a controlling role is called a modulated signal.
Laser modulation can be divided into internal modulation and external modulation.
Internal modulation: It refers to the loading of modulated signals during the laser oscillation process, that is, using modulated signals to change the oscillation parameters of the laser, thereby altering the laser output characteristics to achieve modulation. The methods of internal modulation include: 1. Directly controlling the laser pump power supply to achieve the intensity of the modulated output laser. The strength and presence of the output are all controlled by the power supply. If the signal to be transmitted is used to control the laser power supply, making the current changes through the laser controlled by the signal, then the emitted laser will also be controlled by the signal. 2. Modulation elements are placed inside the resonant cavity, and the physical properties of the modulation elements are controlled by signals to change, thereby altering the parameters of the resonant cavity and changing the laser output characteristics to achieve modulation. The advantage of internal modulation is its high modulation efficiency. The drawback is that since the modulator is placed inside the cavity, it is equivalent to increasing the loss inside the cavity, reducing the output power, and the bandwidth of the modulator is limited by the passband of the resonant cavity.
External modulation: It refers to the placement of a modulator on the optical path outside the laser after the laser is formed, and the physical characteristics of the modulator are changed by the modulation signal. When the laser passes through the modulator, a certain parameter of the light wave will be modulated. The advantage of external modulation is that it does not affect the output power of the laser and the bandwidth of the generator is not limited by the passband of the resonant cavity. The drawback is the low modulation efficiency.
Laser modulation can be classified into amplitude modulation, frequency modulation, phase modulation and intensity modulation, etc. according to its modulation nature. The corresponding common modulators include phase modulators, intensity modulators, etc. Besides the aforementioned electro-optic intensity modulation and electro-optic phase modulation, There are many types of laser modulators, such as transverse electro-optic modulators, electro-optic traveling wave modulators, Kerr electro-optic modulators, acousto-optic modulators, magneto-optic modulators, interference modulators and spatial light modulators, etc.
Post time: May-13-2025