JPH04277687A - Semiconductor laser device and optical amplifier utilizing the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used in optical communications and an optical amplifier using the semiconductor laser device.

0002

2. Description of the Related Art In optical communication systems, devices for amplifying optical signals become important when transmitting optical signals over long distances or branching them. Conventionally, the optical signal was amplified by first converting the optical signal into an electrical signal and amplifying it, and then converting the amplified electrical signal into an optical signal using a light emitting element. However, in recent years, optical amplifiers using optical fibers doped with rare earth ions such as Er have been developed, making it possible to directly amplify signal light using light (pumping light) with a shorter wavelength than the signal light. . For example, as shown in FIG. 4, this optical amplifier is composed of an Er-doped fiber 5 for pumping and a pumping light source 9 consisting of a semiconductor laser element. The wavelength λS of the signal light to be amplified by the communication optical fiber 10 is 1.
In the case of 55 μm, as the excitation light source 9, the oscillation wavelength λP 1
．． A semiconductor laser element with a diameter of around 47 μm is used. At this time, when the 1.55 μm signal light enters the semiconductor laser element of the excitation light source 9, the signal light promotes carrier recombination within the semiconductor laser element, and as a result, a large current flows, causing the semiconductor laser element to may deteriorate. For this reason, an optical isolator 8 is inserted between the excitation light input part of the Er-doped fiber 5 and the excitation light source 9 to prevent the signal light from entering the semiconductor laser element of the excitation light source 9. 6 is an optical coupling lens, and 11 is a signal light source.

0003

[Problems to be Solved by the Invention] However, since the above-mentioned optical amplifier includes an optical isolator, the cost is high, and in addition, it is difficult to incorporate the optical isolator, which hinders productivity and reliability. there were.

0004

[Means for Solving the Problems] The present invention provides a semiconductor laser device that solves the above-mentioned problems and an optical amplifier using the same. A first invention provides a semiconductor laser device in which an optical filter is formed that has a low reflectance for light with a wavelength longer than that of the oscillated light and a high reflectance for light with a longer wavelength than the oscillation light, the optical filter being a semiconductor made of a dielectric multilayer film. The laser device is a second invention. Further, a third invention provides an optical amplifier that pumps an optical fiber doped with rare earth ions using the semiconductor laser device of the first invention as a pumping light source, and uses stimulated emission of the ions to amplify an optical signal in the optical fiber. It is something.

[0005]

[Function] The semiconductor laser device of the present invention has a low reflectance for the oscillated light and a high reflectance for light with a longer wavelength than the oscillated light at the end face from which the oscillated light of the semiconductor laser element is emitted. Since the optical filter is formed, the oscillated light is emitted from the end facet, but light with a longer wavelength than the oscillated light does not enter the end facet from the outside from which the semiconductor laser element emits light. Therefore, the semiconductor laser element will not be deteriorated by such incident light. The optical amplifier of the present invention uses the semiconductor laser device of the above invention as a pumping light source. Then, since the optical filter has a low reflectance for the oscillation light (wavelength λP) of the semiconductor laser element, this oscillation light passes through the optical filter and excites the optical fiber doped with rare earth ions. On the other hand, for the signal light (wavelength λS) from the optical fiber to be amplified, λS > λP
Therefore, the optical filter has a high reflectance, and the signal light does not enter the semiconductor laser element. Therefore, in the optical amplifier of the present invention, there is no need to incorporate an optical isolator between the semiconductor laser device and the rare earth ion-doped optical fiber.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on embodiments shown in the drawings. FIG. 1 is a side view of an embodiment of a semiconductor laser device according to the present invention, in which 1 is a semiconductor laser element,
2 is an optical filter formed on the oscillation end face of the semiconductor laser device, and 7 is an active region. The optical filter 2 is composed of a dielectric multilayer film in which dielectric films 3 having a low refractive index n1 and dielectric films 4 having a high refractive index n2 are alternately laminated. The refractive indices n1 and n2 are set so that they exhibit a low reflectance for the oscillation wavelength λP of the semiconductor laser element 1, and high reflectance for a wavelength λS longer than that wavelength. For example, λP = 1.47 μm, λS = 1.55 μm
For the dielectric film 3, SiO2 (n1 = 1.4
), and the dielectric film 4 is made of Si (n2 = 3.5). Such an optical filter 2 can be formed using a technique such as plasma CVD. FIG. 2 is an explanatory diagram of an embodiment of the optical amplifier according to the present invention, in which 5 is an Er-doped fiber;
6 is an optical coupling lens, and 9 is an excitation light source consisting of the semiconductor laser device of the above embodiment. In this optical amplifier, the wavelength λ
The signal light with S=1.55 μm is reflected by the optical filter 2 of the excitation light source 9. Therefore, there is no need to install an optical isolator between the excitation light source 9 and the Er-doped fiber 5. 11 is a light source for signal light. The semiconductor laser device is not limited to the embodiment shown in FIG. 1, and may be as shown in FIG. 3. That is, most of the oscillation end facet of the semiconductor laser device 1 on which the optical filter 2 is formed, except for the active region 7, is cut so as to be inclined from a direction perpendicular to the oscillation light. Therefore, if the optical fiber is installed so that its optical axis faces in the direction of the oscillated light, resonance will not occur between the optical fiber and the semiconductor laser device of this embodiment. In addition to being used in an optical amplifier as described above, the semiconductor laser device of the present invention may also be used in the following communication systems. That is, increasing capacity by passing light of different wavelengths from two semiconductor laser elements through one optical fiber;
When the semiconductor laser device of the present invention is used as a light source for signal light in a multifunctional communication system, long wavelength light does not enter the semiconductor laser device that is the light source for short wavelength signal light. The signal light source never deteriorates.

[0007]

As explained above, the semiconductor laser device of the present invention has a low reflectance for the oscillation light on the end face from which the oscillation light of the semiconductor laser element is emitted. Since an optical filter having a high reflectance for light is formed, it has the excellent effect of preventing deterioration caused by light having a longer wavelength than the oscillation light entering the semiconductor laser element. Further, in an optical amplifier that uses a semiconductor laser device as a pumping light source, pumps an optical fiber doped with rare earth ions with the pumping light, and uses stimulated emission of the ions, when the semiconductor laser device of the above invention is used as a pumping light source, an optical isolator This has the excellent effect that a reliable optical amplifier can be assembled with high productivity without using.

[Brief explanation of the drawing]

FIG. 1 is a side view of an embodiment of a semiconductor laser device according to the present invention.

FIG. 2 is an explanatory diagram of an embodiment of an optical amplifier according to the present invention.

FIG. 3 is a side view of another embodiment of the semiconductor laser device according to the present invention.

FIG. 4 is an explanatory diagram of a conventional optical amplifier.

[Explanation of symbols]

1 Semiconductor laser element 2
Optical filters 3 and 4 Dielectric film 5 Er-doped fiber 6
Optical coupling lens 7 Active region 8 Optical isolator 9
excitation light source

Claims (3)

[Claims] 1. An optical filter having a low reflectance for the oscillated light and a high reflectance for light with a longer wavelength than the oscillated light is formed on the end face of the semiconductor laser element from which the oscillated light is emitted. A semiconductor laser device characterized by: 2. The semiconductor laser device according to claim 1, wherein the optical filter is made of a dielectric multilayer film. 3. An optical fiber doped with rare earth ions is excited by using the semiconductor laser device according to claim 1 as a pumping light source, and stimulated emission of the ions is used to amplify an optical signal in the optical fiber. optical amplifier.