What exactly is the structure of a laser module?

All semiconductor lasers are generated by focusing the output of a laser diode. Green lasers differ from red ones in that there is no laser diode that directly emits green light; instead, green light is produced by using a crystal for conversion, followed by beam expansion and collimation to achieve a well-focused beam. Let us begin by examining the crystals involved: Nd:YVO4 and KTP. The Nd:YVO4 crystal is currently one of the most effective gain media for LD-pumped all-solid-state lasers. Its excellent properties-including chemical and physical stability, a low lasing threshold, a large stimulated emission cross-section, high slope efficiency, and broad-bandwidth pump absorption-have led to its increasingly widespread application. Recently, high-power, highly stable infrared and green lasers created by combining Nd:YVO4 with KTP crystals have entered industrial production and found broad market application. KTP (Potassium Titanyl Phosphate) crystal: KTP is currently one of the best all-around performers among nonlinear crystals. Its large nonlinear coefficient, high optical damage threshold, chemical stability, extremely high frequency-doubling conversion efficiency (>70%), and relatively low cost have secured its dominant and enduring position in this field; KTP is the premier crystal material, particularly for 1064nm frequency-doubling devices. The process involves using an 808nm LD to pump an Nd:YVO4 crystal to generate 1064nm laser light, which is then frequency-doubled by a KTP crystal to produce 532nm green laser light. Green laser modules are analogous to integrated circuits in electronics; they feature a modular, integrated design that allows for mass production and cost reduction. These green laser modules are fabricated using the popular optical bonding process. Compared to adhesive bonding, this method eliminates optical gaps at the interface, resulting in higher green light output power, superior beam quality, and minimal flicker, thereby enabling stable continuous-wave (CW) output. With a 200 mW diode pump and a crystal measuring 0.8 × 0.8 × 2 mm, the typical green light output power ranges from 5 to 10 mW; however, conversion efficiency depends heavily on the quality of the laser diode and the crystal, with state-of-the-art technology and materials achieving efficiencies exceeding 35%. Due to the ease with which they facilitate the construction of laser resonators, these modules serve as core components in diode-pumped solid-state lasers (DPSSLs).