| 摘要 |
There are provided a wavelength selection device, a wavelength selection laser, and a tunable laser for suppressing adverse effects of non-selected light when selected light is obtained by the wavelength selection device. A linear polarizer is arranged on a side of the wavelength selection filter from which an incoming light enters, and a first faraday element and a second faraday element each for rotating the polarization of light by 45 degrees are arranged at respective locations between the linear polarizer and the wavelength selection filter, and between the wavelength selection filter and a reflection mirror for reflecting light having passed through the wavelength selection filter. After then incoming light has passed through the linear polarizer, selected light passes through the wavelength selection filter and is reflected by the reflection mirror, while non-selected light is reflected by the wavelength selection filter. The selected light and the non-selected light are different in the number of times of passing through the faraday elements before they return to the linear polarizer. Due to the resultant difference in polarization direction thereof, the selected light passes through the linear polarizer, whereas the non-selected light is blocked by the linear polarizer. This makes it possible to accurately take out light of wavelengths allowed to pass through the wavelength selection filter.
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