Fiber laser oscillator having thin filter reflector

An apparatus comprising:

• a first fiber for receiving a lasing light having a selected wavelength band and providing a combined light of the lasing light and a pump light having wavelengths except the selected wavelength band;
• a second fiber for receiving the pump light;
• a first ferrule for holding the first fiber and the second fiber;
• a first lens for collimating light exiting from the first fiber and light exiting from the second fiber;
• a first tube for holding the first ferrule and the first lens;
• a thin film filter for transmitting the lasing light having the selected wavelength band for a first time and reflecting the pump light having wavelengths except the selected wavelength band;
• and
• a reflector for reflecting the lasing light transmitted for the first time through the thin film filter;
• wherein the lasing light reflected by the reflector transmits through the thin film filter for a second time and overlaps with the pump light reflected by the thin film filter;
• and
• wherein the first fiber and the second fiber are disposed symmetrically to an optical axis of the first lens.

A method for combining a lasing light and a pump light comprising:

• providing a lasing light having a selected wavelength band;
• providing a pump light;
• the lasing light having the selected wavelength band being transmitted by a thin film filter for a first time and the pump light having wavelengths except the selected wavelength band being reflected by the thin film filter;
• the transmitted lasing light through the thin film filter for the first time being reflected by a reflector;
• the reflected lasing light by the reflector being transmitted for a second time through the thin film filter;
• the transmitted lasing light through the thin film filter for the second time overlapping with the pump light having wavelengths except the selected wavelength band reflected by the thin film filter.