Intracavity frequency doubling fiber laser

An intracavity frequency doubling fiber laser includes pump sources, optical beam combiners and a bidirectional optical amplifier (6);

• a first fiber collimator (5), a first optical polarization rotating device (4), a polarizer (3), a laser frequency doubling device (2) and a laser cavity mirror (1) being arranged on one side of the bidirectional optical amplifier (6) along an optical path in sequence;
• a second fiber collimator (9), a polarization beam splitting device (10), a second optical polarization rotating device (11) and a reflection device (13) being arranged on the other side of the bidirectional optical amplifier (6) along the optical path in sequence;
• the first and second optical polarization rotating devices being configured to rotate fundamental frequency laser with a polarization direction of 45° in a nonreciprocal manner;
• the laser frequency doubling device (2) being configured to convert the fundamental frequency laser with a frequency of ω into frequency-doubled laser with a frequency of 20;
• the polarization beam splitting device (10) being configured to split the fundamental frequency laser into an S-polarized laser and a P-polarized laser;
• pump light generated by the pump sources being coupled to the bidirectional optical amplifier (6) by the optical beam combiners, and the bidirectional optical amplifier (6) absorbs the pump light and generates, amplifies and outputs the fundamental frequency laser;
• the fundamental frequency laser output from one side of the bidirectional optical amplifier (6) enters the first optical polarization rotating device (4) to be rotated with a polarization direction of 45° in a non-reciprocal manner after being collimated by the first fiber collimator (5), and then enters the polarizer (3);
• the fundamental frequency laser that has been polarized in the same direction as a transmission axis direction of the polarizer (3) enters the laser frequency doubling device (2) through the polarizer (3), part of polarized fundamental frequency laser therein is converted into frequency-doubled laser, and the frequency-doubled laser is output from the laser cavity mirror (1);
• polarized fundamental frequency laser which is not converted into the frequency-doubled laser is reflected back by the laser cavity mirror (1) along the original optical path, reaches the first optical polarization rotating device (4) in the incident manner after passing through the laser frequency doubling device (2) and the polarizer (3) in sequence, rotated with a polarization direction of 45° in the non-reciprocal manner, and then enters the bidirectional optical amplifier (6);
• the fundamental frequency laser output from the other side of the bidirectional optical amplifier (6) enters the polarization beam splitting device (10) in the incident manner after being collimated by the second fiber collimator (9), then enters the second optical polarization rotating device (11) after being transmitted through the polarization beam splitting device (10), rotated with a polarization direction of 45° in the non-reciprocal manner, and then enters the reflection device (13) in the incident manner;
• and it is reflected back by the reflection device (13) to the second optical polarization rotating device (11), rotated with a polarization direction of 45° in the non-reciprocal manner again, and then enters the bidirectional optical amplifier (6) through the polarization beam splitting device (10) and the second fiber collimator (9) in sequence.