| 摘要 |
[Problems] To provide a tunable laser with high reliability and high performance, and of low cost. [Means for Solving Problems] A tunable laser ( 10 ) comprises a double ring resonator ( 11 ) where ring resonators ( 111, 112 ) of different sizes are coupled through a directional coupler ( 122 ), an LD side waveguide ( 13 ) connected at one end ( 131 ) to the ring resonator ( 111 ) through a directional coupler ( 123 ), a reflection side waveguide ( 14 ) connected at one end ( 141 ) to the ring resonator ( 112 ) through a directional coupler ( 123 ), a PLC board ( 15 ) on which the ring resonator ( 111 ) and the like are formed, a high reflection film ( 16 ) provided at the other end ( 142 ) of the reflection side waveguide ( 14 ), an LD chip ( 17 ) having a low reflection film ( 18 ) formed on either of two opposing emission end faces ( 171, 172 ) and coupled optically with the other end ( 132 ) of the LD side waveguide ( 13 ), and film-like heaters ( 191 - 194 ) for varying the resonance wavelength of the double ring resonator ( 11 ).
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