substrate 101 the layer 103 consists of molybdenum oxide formed by for example vapor phase deposition at 630 u00b0 c and is n type with a carrier density of 3 u00d7 10 17 cm u2212 3 a thickness of the layer 103 is 3 0 u03bcm a layer 104 of chromium molybdenum oxide cr 0 1 mo 0 9 o 3 is formed on the layer 103 the layer 104 of chromium molybdenum oxide has a larger bandgap than molybdenum oxide and acts as a cladding layer which confines carrier and light in an active layer of the laser diode although the layer 104 is not intentionally doped it is n type with a carrier density of 6 u00d7 10 16 cm u2212 3 it is formed for example by vapor phase deposition at 600 u00b0 c and its thickness is 3 0 u03bcm a layer 105 of a p type molybdenum oxide is formed on the layer 104 as an active layer of the laser diode 100 the layer 105 is formed for example by vapor phase deposition with doping to a hole density of 1 u00d7 10 17 cm u2212 3 a thickness of the layer 105 is 0 5 u03bcm a layer 106 of chromium molybdenum oxide cr 0 1 mo 0 9 o 3 is formed on the layer 105 a layer 106 has a larger bandgap than the active layer 105 of molybdenum oxide and acts as a cladding layer of the laser diode 100 the layer 106 is formed for example by vapor phase deposition and has a thickness of 3 0 u03bcm the layer 106 is doped for example.