Patent ID: 6996140

Claim:
A laser apparatus for nonlinear frequency conversion of light comprising: a) a semiconductor laser diode having a reflective back facet and a front facet with a reflection coefficient of less than about 1% for emitting multifrequency laser radiation in multiple longitudinal modes and an essentially single spatial mode along an optical path; b) a partially reflecting filter having a reflection bandwidth b disposed to receive the multifrequency laser radiation from the front facet and to reflect a first portion of the multifrequency laser radiation of bandwidth b towards the front facet, for confining the operation of the semiconductor laser diode within said bandwidth b and for transmitting a second portion of the multifrequency laser radiation along the optical path; c) a nonlinear optical element having nonlinear optical conversion bandwidth c disposed to receive the second portion of the multifrequency laser radiation for nonlinear frequency conversion of the multifrequency laser radiation and for producing a frequency-converted multifrequency radiation; wherein said partially reflecting filter and the back facet of the semiconductor laser diode form a cavity having a longitudinal mode spacing a, wherein the reflection bandwidth b is smaller than 3c and the longitudinal mode spacing a is substantially smaller than the nonlinear optical conversion bandwidth c and the reflection bandwidth b, for enabling nonlinear frequency conversion of a plurality of longitudinal modes of the extended cavity.