NOVEL PASSIVELY Q-SWITCHED LASER
Passively Q-switched lasers and short wave infrared (SWIR) electro-optical systems including such lasers. A passively Q-switched laser may include a gain medium (GM) having a stimulated emission cross section σ SE , a saturable absorber (SA) having an absorption cross section (σ a ) which is less than three times the σ SE of the GM, and an optical resonator within which the GM and the SA are positioned, the optical resonator comprising a high reflectivity mirror and an output coupler, wherein at least one of the high reflectivity mirror and the output coupler comprises a curved mirror, directing light within the optical resonator such that an effective cross-section of a laser mode within the SA (A SA ) is smaller than a cross-section of a laser mode within a Rayleigh length of the pump (A GM ).
1 . A passively Q-switched laser, comprising:
a gain medium (GM) having a stimulated emission cross section σ SE ;
a saturable absorber (SA) having an absorption cross section (Ga) which is less than three times the σ SE of the GM; and
an optical resonator within which the GM and the SA are positioned, the optical resonator comprising a high reflectivity mirror and an output coupler,
wherein at least one of the high reflectivity mirror and the output coupler comprises a curved mirror, directing light within the optical resonator such that an effective cross-section of a laser mode within the SA (A SA ) is smaller than a cross-section of a laser mode within a Rayleigh length of the pump (A GM ).
2 . The passively Q-switched laser according to claim 1 , wherein the GM is made of neodymium-doped yttrium aluminum garnet (Nd:YAG) and wherein the SA is made of cobalt-doped YAG (Co 2+ :YAG).
3 . The passively Q-switched laser according to claim 1 , wherein the GM is made of neodymium-doped yttrium orthovanadate (YVO 4 ) and wherein the SA is made of a three-valence vanadium-doped yttrium aluminum garnet (V 3+ :YAG).
4 . The passively Q-switched laser according to claim 1 , wherein the GM is made of neodymium-doped yttrium orthovanadate (YVO 4 ) and wherein the SA is made from cobalt-doped YAG (Co 2+ :YAG).
5 . The passively Q-switched laser according to claim 1 , wherein the high reflectivity mirror and the output coupler are rigidly coupled to the GM and to the SA, such that the passively Q-switched laser is a monolithic microchip passively Q-switched laser.
6 . The passively Q-switched laser according to claim 1 , wherein the high reflectivity mirror is a concave mirror.
7 . The passively Q-switched laser according to claim 1 , wherein both the high reflectivity mirror and the output coupler are concave mirrors.
8 . The passively Q-switched laser according to claim 7 , wherein the curvatures of the concave high reflectivity mirror and of the concave output coupler are such that the highest energy density is within the middle 60% of the optical resonator.
9 . The passively Q-switched laser according to claim 1 , wherein a diameter of the SA is smaller than a diameter of the GM, and wherein the SA is surrounded by another material for releasing heat from the optical resonator.
10 . The passively Q-switched laser according to claim 1 , further comprising at least one end-pumping light source and optics for focusing light of the end-pumping light source into the optical resonator.
11 . The passively Q-switched laser according to claim 1 , wherein the GM and the SA are polycrystalline materials.
12 . The passively Q-switched laser according to claim 1 , further comprising undoped YAG in addition to the GM and the SA for preventing heat from accumulating in an absorptive region of the GM.
13 . The passively Q-switched laser according to claim 1 , wherein the GM and the SA are implemented on a single piece of crystalline material doped with neodymium and with at least one other material.
14 . The passively Q-switched laser according to claim 1 , wherein the passively Q-switched laser emits light through the output coupler within wavelengths range of 1,300 nm and 1,500 nm.
15 . A short wave infrared (SWIR) electro-optical system comprising the passively Q-switched laser according to claim 1 and further comprising a SWIR photodetector array sensitive to the wavelength of the passively Q-switched laser for detecting reflections of laser illumination off at least one illuminated object.
16 . A short wave infrared (SWIR) electro-optical system comprising the passively Q-switched laser according to claim 1 and further comprising a time of flight (ToF) SWIR sensor sensitive to the wavelength of the passively Q-switched laser, a controller operable to synchronize operation of the ToF SWIR sensor and the passively Q-switched laser, and a processor operable to process detection, by the ToF SWIR sensor, of reflections of laser illumination of the passively Q-switched laser, for determining a distance to at least one object in a field of view of the SWIR electrooptical system.