Composite photonic structure element, surface emitting laser using the composite photonic structure element, wavelength conversion element, and laser processing device using the wavelength conversion element

A wavelength conversion element comprising:

• a bipolar multilayer crystal H formed by alternately laminating a plurality of sets of an active layer having a nonlinear effect for converting a fundamental wave into a second harmonic and an inactive layer free of the nonlinear effect;
• and
• first and second reflector multilayer films K1, K2, each formed by laminating a plurality of sets of two kinds of thin films having different refractive indexes, for reflecting the fundamental wave;
• wherein the first and second reflector multilayer films K1, K2 are connected to both sides of the bipolar multilayer crystal H;
• wherein the bipolar multilayer crystal H is constructed such that the alternately laminated plurality of sets of the active and inactive layers invert layers therewithin;
• wherein the fundamental wave enters from one of end faces and is reciprocally reflected between resonators equipped with the first and second reflector multilayer films K1, K2 so as to enhance an intensity within the bipolar multilayer crystal H;
• and
• wherein the fundamental wave is converted into the second harmonic in the active layer, and the second harmonic is taken out from the other end face.

A wave conversion element comprising:

• a bipolar multilayer crystal H formed by alternately laminating a plurality of sets of an active layer having a nonlinear effect for converting a fundamental wave at a wavelength λ into a second harmonic at a wavelength λ/2, a refractive index n with respect to the fundamental wave, and a thickness d and an inactive layer, free of the nonlinear effect, having a refractive index m with respect to the fundamental wave and a thickness e, the plurality of laminated sets being joined together such as to invert layers in an intermediate portion located near a center;
• and
• first and second reflector multilayer films K1, K2, each formed by laminating a plurality of sets of two kinds of thin films having different refractive indexes and being free of the nonlinear effect, for reflecting the fundamental wave;
• wherein the first and second reflector multilayer films K1, K2 are connected to both sides of the bipolar multilayer crystal H, so as to constitute a K1HK2 structure;
• wherein the bipolar multilayer crystal H and the first and second reflector multilayer films K1, K2 are constructed such that, when the fundamental wave enters from one of end faces, an electric field is increased in the first reflector multilayer film K1, the electric field is increased on the first reflector multilayer film K1 side of the bipolar multilayer crystal H, the electric field is maximized in the intermediate portion of the bipolar multilayer crystal H, the electric field is decreased on the second reflector multilayer film K2 side of the bipolar multilayer crystal H, the electric field is decreased in the second reflector multilayer film K2, and a transmitted wave having substantially the same intensity as that of the fundamental wave having entered therein is emitted from the other end face;
• and
• wherein the fundamental wave enhanced in the active layer in the bipolar multilayer crystal H is caused to generate the second harmonic, and the second harmonic is taken out from the other end face.