Importance

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Abstract

The present invention relates to an external cavity type laser provided with a wavemeter capable of precisely measuring a wavelength of a laser beam based on a transmission wavelength band of a wavelength selective filter inserted into a cavity regardless of a driving current of a laser diode chip. The external cavity type laser apparatus includes: a laser diode chip 100 emitting a laser beam; a beam feedback partial reflection mirror 500 reflecting a portion of the beam emitted from the laser diode chip 100 to feed the beam back to the laser diode chip 100; a collimating lens 200 installed on a path of a beam between the laser diode chip 100 and the beam feedback partial reflection mirror 500 to collimate the beam emitted from the laser diode chip 100; a 45-degree partial reflection mirror 300 converting a laser beam moving in parallel with a package bottom surface into a laser beam moving perpendicularly to the package bottom surface; a wavelength selective filter 400 transmitting a beam having a selected specific wavelength therethrough; a beam strength monitoring photodiode 600 disposed on a path of a beam moving from the collimating lens 200 to the 45-degree partial reflection mirror 300 and transmitting through the 45-degree partial reflection mirror 300; and a wavelength monitoring photodiode 700 disposed on a path of a beam moving from the wavelength selective filter 400 to the 45-degree partial reflection mirror 300 and transmitting through the 45-degree partial reflection mirror 300. A magnitude of a photocurrent flowing to the wavelength monitoring photodiode 700 is changed depending on a strength of a beam output oscillated in the laser diode chip 100 and a reflectivity at the wavelength selective filter 400, and a photocurrent flowing to the beam strength monitoring photodiode 600 is determined by the strength of the beam output outputted from the laser diode chip 100. Therefore, a value obtained by dividing the photocurrent flowing to the wavelength monitoring photodiode 700 by the photocurrent flowing to the beam strength monitoring photodiode 600 depends on only the reflectivity at the wavelength selective filter 400. Therefore, the value obtained by dividing the photocurrent flowing to the wavelength monitoring photodiode 700 by the photocurrent flowing to the beam strength monitoring photodiode 600 provides information on the wavelength of the laser beam based on the transmission band wavelength of the wavelength selective filter 400, and the wavelength of the laser beam may be figured out by measuring the value, and may be very precisely determined to be a predetermined wavelength.

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First Claim