JPH04165685A - Laser beam source of variable wavelength - Google Patents

Abstract

PURPOSE:To obtain a laser beam source of a wide variable wavelength utilizing a rare earth element-doped optical fiber amplifier as an external oscillator by a method wherein the laser beam source is provided with a wavelength multiplexer for making wave combined light incide in the first end part of an optical fiber and a half mirror, which is mounted to the second end part of the optical fiber. CONSTITUTION:A laser beam source is provided with a rare earth element-doped optical fiber 1, an excitation light source 2 for exciting the fiber 1, a wave- length selecting element 3 for selecting a wavelength, a wavelength selecting element control part 4 for controlling the element 3, a wavelength multiplexer 5, which combines return light from the element 3 with output light of the light source 2 and makes the wave combined light incide in an end part 1A of the fiber 1, and a half mirror 6 which is mounted to an end part 1B of the film 1. Thereby, as a rare earth element-doped optical fiber amplification and the element 3 are adopted, the laser beam source of a wide variable wavelength can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser light source whose emission wavelength can be changed.

[Prior Art] For future applications such as coherent YT communication and wavelength multiplexed optical memory, a technology that can quickly and stably vary the wavelength over a wide range will be required.

Conventional techniques use semiconductor lasers and utilize changes in bandgap energy and refractive index. In a semiconductor laser, both the bandgap energy and the refractive index depend on temperature, so the wavelength can be changed depending on the temperature.

Next, the relationship between wavelength and temperature of a semiconductor laser will be explained with reference to FIG.

The part that changes continuously in the curve in Figure 2 is due to the change in refractive index, and the rate of temperature change is 50 to 60 pm.
/'C, maximum continuous variable range is 0.4. It is about nm.

Further, the discontinuously changing portion is called longitudinal mode hopping, which occurs because the energy gap shift (0,2 to Q, 5 nm/'C) due to temperature change is larger than the refractive index shift.

Due to mode hopping, it may not always be possible to tune to the desired wavelength.

Utilizing the phenomenon shown in Figure 2, lasers that utilize the interference effect of a composite resonator, or lasers with a phase control region such as DFB lasers and DBR lasers, are made into multi-electrode structures, and the current flowing there is controlled to achieve wavelength control. There is an integrated type that changes the Also,
If an external resonator is constructed by using a wavelength-selective optical element such as a diffraction grating or a combination of a mirror and an etalon in a semiconductor laser, it is possible to oscillate in any longitudinal mode within the gain width of the laser. In this case, the oscillation mode can be changed by rotating the diffraction grating or etalon.

Even in this method, the range of variable wavelength is determined by the gain width of the laser, and the limit is several rxm. Furthermore, since the laser beam is optically controlled, the structure becomes mechanically fine, making adjustment difficult.

[Problem to be solved by the invention] In the conventional technology, since changes in the bandgap energy and refractive index of a semiconductor laser are used, the variable width is narrow,
Furthermore, due to mode hopping, it may not always be possible to tune to the required wavelength.

The present invention aims to provide a laser light source with a wide tunable wavelength by using an optical fiber amplifier doped with a rare earth element as an external resonator.

[Means for Solving the Problems] In order to achieve this object, the present invention includes an optical fiber 1 doped with a rare earth element, an excitation light source 2 that excites the optical fiber 1, and a wavelength selection element 3 that selects a wavelength. , a wavelength selection element control unit 4 that controls the wavelength selection element 3, and combines the return light from the wavelength selection element 3 and the output light of the excitation light M, 2,
The optical fiber 1 includes a wavelength multiplexer 5 that inputs multiplexed light into the @ section IA of the optical fiber, and a half mirror 6 that is attached to the end 1B of the optical fiber 1.

[Function] Generally, when excitation light with a certain wavelength is incident on an optical fiber doped with rare earth elements, the optical fiber enters an excited state and exhibits fluorescence characteristics over a relatively wide range of wavelengths based on its energy level. In this state, when light with a specific wavelength within the wavelength range that has fluorescent characteristics is input into the optical fiber from the outside, a stimulated emission phenomenon occurs and the light can be amplified.

Next, the configuration of the optical fiber amplifier will be explained with reference to FIG. FIG. 3A is a block diagram of an optical fiber amplifier, in which 1 is an optical fiber, 2 is a pumping light source, 5 is a wavelength multiplexer, and 7 is a signal light.

The optical fiber 1 is an optical fiber doped with erbium as a rare earth element, and the excitation light source 2 excites the optical fiber 1. The wavelength multiplexer 5 combines the output light of the signal light 7 and the pump light [2]. For example, a 1.554 μm light source is used as the signal light 7.

FIG. 3A shows the output spectrum of the signal light 7, and FIG. 3 shows the spectrum of the output light from the optical fiber 1 when the signal light 7 is off and only the excitation light source 2 is on. Figure 3 shows the output spectrum of the optical fiber 1 when the signal light 7 is turned on in the state shown in Figure 3.

The level difference between the signal lights in Figure 3A and Figure 3A is the gain of the optical fiber amplifier in Figure 3A. Normally, a gain of about 20 dB can be obtained, and amplification can be performed within the range in which the fluorescence spectra shown in Figure 3 appear.

Next, a configuration diagram of a variable wavelength laser light source according to the present invention will be explained with reference to FIG.

3 in FIG. 1 is a wavelength selection element, 4 is a wavelength selection element control section, and the other parts are the same as in FIG. 3A. Wavelength table'i
A wavelength selection element 3 is installed at the end 5A of the F'1 device 5.
I get kicked. The end IA of the optical fiber 1 is attached to the end 5B of the wavelength multiplexer 5, and the half mirror 6 is attached to the end 1B of the optical fiber 1.

In FIG. 1, the optical fiber amplifier in FIG. 3A is used as a component, and a part of the fluorescence spectrum in FIG. Therefore, it is possible to amplify in that wavelength range. This amplification action works instantaneously, and finally oscillates,
Emits a strong 9 as a laser beam. In order to return light of an arbitrary wavelength to the optical fiber 1-, the angle of the wavelength selection element 3 is controlled.

[Effects of the Invention] According to the present invention, since an optical fiber amplifier doped with a rare earth element and a wavelength selection element are employed, it is possible to provide a laser light source with a wide variable wavelength range.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a variable wavelength laser light source according to the present invention, FIG. 2 is a diagram illustrating the relationship between wavelength and temperature of a semiconductor laser, and FIG. 3 is a block diagram of an optical fiber amplifier. ]... Optical fiber, 2... Excitation light source,
3...Wavelength selection element, 4...Wavelength selection element control section, 5...Wavelength multiplexer 5.6...
...Half Mirror-0 agent patent attorney Kin Omata
Figure 1 0m Temperature Figure 2

Claims (1)

[Claims] 1. An optical fiber (1) doped with a rare earth element, an excitation light source (2) that excites the optical fiber (1), a wavelength selection element (3) that selects a wavelength, and a wavelength selection element. (3) Wavelength selection element control section (4
), and combines the return light from the wavelength selection element (3) and the output light of the excitation light source (2), and connects the light to the first end (1A) of the optical fiber (1).
A variable wavelength laser light source characterized by comprising: a wavelength multiplexer (5) that inputs multiplexed light into the optical fiber (1); and a half mirror (6) attached to the second end (1B) of the optical fiber (1). .