Highly Efficient 1.8 Micrometre Band Broadband Amplified Spontaneous Emission Light Source Using Double-Pass Configuration

We propose an amplified spontaneous emission (ASE) light source using a double-pass configuration as a broadband light source operating in the 1.8 µm band. By using the double-pass configuration, the ASE light amplified in the Tm-doped fluoride fiber (TDF) is reflected by a mirror and amplified again, thereby improving the efficiency of the ASE light source and the output spectrum characteristics. In this report, we compared the commonly used single-pass configuration with the double-pass configuration in terms of the pumping method (forward or backward pumping) and TDF length. In addition, the double-pass configuration was also compared in terms of the presence or absence of reflection of the pump light. The results showed that the double-pass configuration with backward pumping and reflection of pump light has the highest efficiency and output characteristics regardless of the TDF length, and a bandwidth (intensity of over −40dBm/nm) of 271.4 nm was achieved with pumping power of 10 mW.