Indium gallium nitride (InGaN) laser diodes can directly produce laser diodes that emit blue light, but it is difficult to produce laser diodes that emit green light directly, especially those that are considered to be truly green: early green laser diodes Usually has a slight cyan projection.
As a commercial pioneer of green InGaN laser diodes, OSRAM Opto Semiconductors has been promoting the development of long-wavelength laser diodes. A laser based on InGaN-based direct-emitting green light has been introduced, with wavelengths from 510 to 530 nm, which can be used for micro-projection. And other red, green, blue (RGB) or green laser applications. (Osram also produces blue laser diodes.)
The new lasers are available in TO38 ICut or TO56 packages (with a flange diameter of only 3.8 mm) with integrated photodiodes, typically with a parallel divergence angle of 7°and a vertical divergence angle of 22°, small enough to pass The relatively simple optics are cyclized and collimated. Osram says this is an important feature for microelectromechanical systems (MEMS) based projectors where the color component of each pixel is higher than the emission time from the laser diode.
The competition for existing small-sized green lasers is mainly in the form of frequency-doubled diode-pumped solid-state (DPSS) lasers, which are usually found in the first green laser pointer. These lasers are relatively complex, including an infrared pump laser diode for pumping solid state lasers, and a nonlinear optical crystal for doubling the frequency of the resulting IR light into a green laser. In contrast, a diode that directly emits lasers contains only one direct-emitting laser diode.
Osram’s new two green laser diodes, PL520B and PL 520, have slightly different wavelength ranges. According to Osram, the single-mode PL 520 laser diode has an output wavelength of 515 to 530 nm and an optical output power of 50 mW. The current efficiency is usually 5% to 6%. These lasers operate over a temperature range of up to 85℃ without active cooling.
Direct emission of green laser diodes facilitates the implementation of practical high-power embedded projectors and may result in the termination of frequency-doubled DPSS lasers in small projectors. Osram says these lasers can also be used for laser performance because their high beam quality can show very fine structures over considerable distances. In addition, the laser’s high thermal stability and small size laser diodes are two highlights for projectors. For applications in construction engineering, such as point or line projection lasers in rangefinders used by construction workers, further measurement distances can be achieved because green light has a greater visible range than red light at the same optical power.
