Patent ID: 6876685

Claim:
A semiconductor laser device comprising: a semiconductor laser element; a window allowing light rays emitted from said semiconductor laser element to transmit there through; and a photodetector for detecting a portion of the emitted light that is reflected by said window, wherein said photodetector is placed at an angle with respect to a horizontal plane of the device; and wherein said photodetector is angled with respect to the horizontal plane of the device according to the following equation: lg < lga = { lpg + ( ( la / 2 ) × ( lpg / leg ) + la / 2 + lpa ) × tan ⁢ ⁢ θ PD 1 - tan ⁢ ⁢ θ PD × tan ⁢ ⁢ θ a } × { tan ⁢ ⁢ θ a + tan ⁡ ( 2 ⁢ ⁢ θ PD + θ a ) } Equation ⁢ ⁢ 1 wherein a reference point is set as a contact point on said window and a vertical line extends from a light emitting point of said semiconductor element perpendicular to said window; and wherein lga indicates a distance between said photodetector and the reference point on said window where light reflected from said photodetector strikes, and lg indicates a distance between the reference point and an outermost circumference of said window, wherein the relationship between lga and lg is such that lga>lg; and wherein θ a =tan −1 (la/2leg), and the value of θ PD satisfies the equation and θ PD represents an angle of inclination of said photodetector, lpg represents a distance between said window and said photodetector, leg represents a distance between the emission end face and said window, la represents a distance between the emission point and the outermost surface of said semiconductor laser element, lpa represents a distance between the emission point and a supporting point of inclined photodetector and wherein θ a ≠0 and θ PD ≠0.