1. Field of the Disclosure
The present disclosure relates to a vertical external cavity surface emitting laser (VECSEL) and a display apparatus employing the same, and more particularly, to a VECSEL having an improved mirror that forms an external cavity to modulate an emitted laser beam and a display apparatus employing the same.
2. Description of the Related Art
VECSELs increase a gain region by adopting an external mirror instead of an upper mirror for a Vertical Cavity Surface Emitting Laser (VCSEL) and obtain a high output power of several to several tens of watts (W) or higher.
FIG. 1 is a schematic diagram illustrating the optical arrangement of a conventional end-pumped VECSEL. Referring to FIG. 1, the conventional VECSEL includes a pumping unit providing a pump beam, a laser chip 11 that is excited by a pump beam to emit a laser beam, and first and second mirrors 17 and 19 that are located outside the laser chip 11 and form an external cavity. The pumping unit includes a pumping light source 1 and a collimating lens 5 collimating a pump beam emitted by the pumping light source 1 and provides a pump beam to a portion of the laser chip from which a laser beam is emitted.
A heat sink 13 is disposed on one surface of the laser chip 11 and dissipates heat generated by the laser chip 11.
The first mirror 17 is separated from the laser chip 11 and is obliquely disposed relative to an axis of incident light emitted by the laser chip 11. The first mirror 17 has a concave reflecting surface 17a facing the laser chip 11 and the second mirror 19. Thus, the first mirror 17 prevents a laser beam resonating between the second mirror 19 and the laser chip 11 from diverging. The second mirror 19 faces the first mirror 17 and reflects light from the first mirror 17 back into the first mirror 17.
A birefrigent filter 15 is disposed between the first mirror 17 and the laser chip 11 and filters out all but a laser beam having a predetermined wavelength. A Second Harmonic Generation (SHG) crystal 21 is disposed between the first and second mirrors 17 and 19 and converts the laser beam emitted by the laser chip 11 to its half wavelength beam.
The conventional VECSEL having the above-mentioned configuration does not have a built-in modulator for modulating laser output power. Thus, the conventional VECSEL requires an external light modulator, such as an acoustic light modulator, that controls laser output power corresponding to an image to be projected or a color wheel when it is used as a scanning light source for each color in a laser display apparatus.