JPH0354529A - Waveguide amplifier made of glass added with rare earth element - Google Patents

Abstract

PURPOSE:To form the waveguide amplifier of a high gain and to obtain the higher output of an implantation synchronization type semiconductor laser as well as to stabilize the oscillation wavelength thereof by using the above- mentioned laser as a pumping source. CONSTITUTION:The waveguide amplifier is constituted of the flush waveguide consisting of glass and the implantation synchronization type semiconductor laser 7 which is synchronized with the light of a reference wavelength stabilizing semiconductor laser 31 and is stabilized in the wavelength is inserted to the intermediate point of the waveguide. The laser 7 is the pumping source and is synchronized with the wavelength of the output light of the reference wavelength stabilizing semiconductor laser 31 implanted via a directional coupler 20, by which the wavelength of the output light is stabilized. The output light of this laser 7 is inputted into a core 4 and is propagated in a core 3 via a ring resonator 5. The light is propagated in the core 4 via a ring oscillator 6 and is inputted to the laser 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a glass waveguide amplifier doped with rare earth elements. [Prior Art] Research into optical fiber amplifiers and lasers in which rare earth elements are added to the optical fiber core has been actively conducted.
It has started to attract attention as an amplifier and laser for light wave communication.

Conventionally, as an optical fiber amplifier, as shown in Fig. 7,
Signal light is propagated in an optical fiber 32 doped with the rare earth element Er, and pumping light is combined with the optical fiber coupler 33 in the propagation direction of the signal light to form a population inversion state. Amplify and output II! A method of separating the excitation light using an optical fiber capacitor 34 is being considered (Kimura, Nakazawa: Oscillation characteristics of optical fiber lasers and their application to optical communications. Laser Society Research Group, RTM
-87-16. PP. 31-37. January 1988).

[Problems to be solved by the invention] The optical fiber amplifier and laser have (1) a core system of 10
Because it has a small diameter of about ALl1, the pumping power density increases and the pumping efficiency increases; (2) the interaction length can be long; and (3) in the case of silica-based optical fibers, the loss is extremely low. It has the characteristics of

However, semiconductor lasers. For those who are trying to construct a system that includes a photodetector, an optical anomalous circuit, an optical branching/coupling circuit, an optical switch circuit, an optical multiplexing/demultiplexing circuit, etc.
Since each component is an individual component, it is difficult to downsize and reduce loss. In addition, since the optical axis of each individual component must be adjusted and arranged individually, it takes an enormous amount of adjustment time, increases costs, and reduces reliability.
There were also issues such as: Furthermore, in order to achieve high gain characteristics, it is necessary to increase the output of the pumping light source, but there is also the problem that a pumping light source with a high output is expensive.

Furthermore, the aIj problem in which the gain of the amplifier fluctuates due to a slight change in the oscillation wavelength of the pumping light has also been a serious problem in building a practical system. This is because the wavelength characteristics of the absorption of excitation light in optical fibers doped with rare earth elements are extremely sharp. Therefore, it is necessary to highly stabilize the wavelength of the excitation light source, but this is extremely effective. The problem was that the circuit construction was also complicated. The purpose of the present invention is to solve the problems of the prior art described above,
Small size, low loss, high gain. Our goal is to provide low-cost and reliable amplifiers. [Means for Solving the Problems] In order to achieve the above object, the rare earth element-doped glass waveguide amplifier of the present invention combines pumping light from the input opening of the rare earth element-doped glass waveguide through which signal light propagates. , an elliptical glass waveguide amplifier that extracts the pumping light from the output side of the waveguide, in which an injection-locked semiconductor laser is used as the pumping light source. In this case, preferably, the coupling of the excitation light to the rare earth element-doped glass waveguide and the extraction of the excitation light from the waveguide are performed through a resonator such as a ring resonator or a directional coupler. More preferably, the excitation light propagation path has a feedback loop structure. In addition, a laser beam with an amplifier function is used for the injection-locked semiconductor laser, and is synchronized with the wavelength of the output light of the standard wavelength-stabilized semiconductor laser light source.

Although the rare earth element-doped glass waveguide amplifier of the present invention is constructed of a planar 411-structured glass waveguide, the rare-earth element-doped glass waveguide and the resonator for coupling and extraction of excitation light may be constructed of an optical fiber structure. It can also be created with

[Function] Signal light is propagated in a glass waveguide doped with rare earth elements, and a resonator is provided on the input side of the waveguide, and the output light of the injection-locked semiconductor laser is used as excitation light within the waveguide. The wavelength of the pumping light can be stabilized and the output can be achieved by coupling the output of the waveguide to a conventional resonator, extracting the pumping light, and inputting it to the input section of the injection-locked semiconductor laser. High gain by increasing light. A highly stable intensifier is realized. Further, by forming the above structure using a glass waveguide having a Brener structure, miniaturization and low loss can be achieved. Furthermore, since the Grainer-based glass waveguide can be easily realized by applying a semiconductor process, lower costs and higher reliability can be expected.

[Example] Figures 1 and 2 show examples of the rare earth element-doped glass waveguide amplifier of the present invention. This consists of a buried glass waveguide, and an injection-locked semiconductor laser 7 whose wavelength is stabilized by being synchronized with the light of the standard wavelength-stabilized semiconductor laser 3l is inserted in the middle of this glass waveguide. ing. FIG. 1 shows a side view of the waveguide amplifier, and FIG. 2 shows its I[-■ cross section. Let's start with the configuration of F#1. Substrate l (for example, Si 2 , Si 02 glass, glass containing a refractive index controlling additive in S 102 , Ga As , In P,
buffer layer 2 (refractive index nb) on top of sapphire etc.
is formed. This buffer layer 2 includes Si02 or Si02 with P, B, Ti, Ge, AJ, Zn.
containing at least one refractive index controlling additive such as
etc. are used. A guide for propagating the optical signal on this buffer layer 2, that is, a core 3.4, a ring resonator 5
．． 6 is formed. In this embodiment, the cores 3.4 are formed parallel to each other and the ring resonator 5.6 is located between the cores 3.4. These guides 3~
6 has a substantially rectangular cross section, and its refractive index nIV is set such that nv > nb with respect to the refractive index nb of the buffer) C42.

The core 3 contains rare earth elements (1.:r,
S102 glass (Si 02
, or Si 02 ) containing at least one type of the refractive index controlling additive 713.

The rare earth element to be added into the core 3 is
An element is selected that has fluorescent properties at the wavelength λst of the signal light to be removed.For example, as the wavelength λS, the wavelength 1.
When the 53 μl band is used, the rare earth elements include Er,
Alternatively, a material in which both Er and Yb are added can be used.

For the core 4 and the ring resonators 5 and 6, the above S102 glass or the same glass as the core 3 can be used.

The entire area including the buffer layer 2 and core 3.4 is covered with a cladding 8, which has a refractive index nc
is selected so that nW is lower than nW, and is made of the sroz glass. The ring resonators 5 and 6 are designed to resonate at the oscillation wavelength λp of the injection-locked semiconductor laser 7, and the ring resonators 5 and 6 are designed to resonate at the oscillation wavelength λp propagating within the core 4 (3).
It has the R ability to selectively couple the optical signal of the core 3 (4) into the core 3 (4). The injection-locked semiconductor laser 7, which is arranged so as not to resonate with the optical signal of the wavelength λS, is a pumping light source and serves as a reference wavelength-stabilized semiconductor laser injected via the directional coupler 20. The wavelength of the output light is synchronized with the wavelength of the output light of No. 31, and the wavelength of the output light can be stabilized. The output light of this injection-locked semiconductor laser 7 is directed into the core 4 by an arrow 11.
It is inputted as shown in FIG. is input into . By configuring the feedback loop as described above, (1) the oscillator wavelength λp can be stabilized, (2) the injection-locked semiconductor (e) laser 7 can have amplification R capability, and higher We can expect the following characteristics: (3) As a result, a stable and high-gain glass waveguide amplifier will be realized. In addition, the entire amplifier can be made smaller. Furthermore, as is already clear, since a finner structure is used, this glass waveguide amplifier is capable of forming a glass film, buttering the glass film (photolithography and dry etching process), forming a glass film, and It can be manufactured through a single semiconductor process such as cutting and polishing, and can be expected to significantly reduce cost through mass production. Furthermore, the signal light and excitation light transmission waveguide 3, Iij11
Light transmission waveguide 4. The ring resonators 5 and 6, the directional coupler 20, and the injection-locked semiconductor laser 7 can be arranged with mask precision, so each component can be coupled with low TFL loss, and reliability is improved. can also be improved. In addition, the inter-injection semiconductor laser 7
A lens, a refractive index matching agent, or the like may be used to couple the input/output part of the core 4 with the core 4 in order to achieve high coupling efficiency.

Figures 3 and 4 show another practical example of the rare earth element-doped glass waveguide amplifier of the present invention. This is the second
In place of the ring resonators 5 and 6 in the figure, a directional coupler 1
4 and 15 are used to couple the excitation light l1 to the core 3, and also cause the excitation light propagating within the core 3 to enter the core 4. Also in this embodiment, the signal light propagating within the core 3 is not coupled to the core 4. As in the case of FIG. 1, the signal light 9 is amplified as it propagates within the core 3 and is taken out as a signal output light 10. That is, excitation light is coupled into the core 3 through the directional coupler 14, and as the excitation light 12 propagates within the core 3, it is absorbed by the rare earth element and increases the energy unit. This causes population inversion, and the signal light 9 is amplified by stimulated emission.
This amplification degree depends on the waveguide length of the core 3, the output value of the excitation light, and the doping concentration of the rare earth element.

In the case of the present invention, by increasing the doping concentration of rare earth elements and increasing the excitation light output value, it is possible to achieve a small size. This realizes a high-gain amplifier. The injection-locked semiconductor laser 7 can be synchronized with the wavelength of the stable reference semiconductor laser 31, or by forming the feedback loop as described above, or by combining it with an injection-locked amplifier. Since it is more stable and easy to obtain large output, it is possible to realize a rare earth-doped glass waveguide amplifier with high gain and extremely little gain fluctuation. FIG. 5 shows another embodiment of the rare earth element-doped glass waveguide amplifier of the present invention. This is an example in which an optical fiber structure is used as the glass waveguide instead of a planar one.

That is, an optical fiber 16 whose core is doped with a rare earth element is used as a waveguide for propagating the signal light and pumping light l2, and the optical fiber shape direction is used as a directional coupler for coupling and extracting the pumping light. using the optical couplers 17 and 18, and as a waveguide for the propagation of the excitation lights 11 and 13,
This uses an optical fiber 19. Further, the output light of the reference wavelength-stabilized semiconductor laser 31 is input to the injection type semiconductor laser 7 through the optical fiber type directional coupler 29. Although it is difficult to achieve miniaturization and low loss with a configuration using this optical fiber, it is possible to achieve high gain. The present invention is not limited to the above actual knee example. First, as a glass waveguide with a planar structure, in addition to the buried type, there are ridge type and loaded type. It may also be realized using a conventionally well-known waveguide structure such as a raised type. Si02 on substrate 1
When glass is used, the buffer layer 2 does not need to be formed.

Alternatively, a rectangular hole may be dug in the Si02 glass substrate, and the cores 3 and 4 may be formed in the groove. As a resonator for coupling or extracting excitation light into a rare earth element-doped glass waveguide, in addition to a ring resonator and a directional coupler, there are also a Taber type directional coupler and a fused spread type resonator. Optical fiber couplers, piconic force taper type optical fiber couplers, etc. may also be used. The present invention is also suitable for amplifying multiple transmission lines. That is, as shown in FIG. 6, when amplifying the optical signal propagating within the two doped cores 3 and 21, the output light of one standard wavelength-stabilized half-barrel laser 31 is Y-branched. The wavelength of the semiconductor laser 31 is synchronized by dividing the wavelength into two by the coupler 30 and inputting the input to the respective injection-locked semiconductor lasers 7 and 25. This stabilizes the wavelength, and by making the feedback loops elliptical, it is possible to further stabilize the wavelength and increase output, thereby realizing a high-gain amplifier. In addition, in FIGS. 1 to 6, the excitation light does not necessarily have to form a feedback loop. The reason is that if the rare earth element-doped cores 3 and 21 are sufficiently long, the feedback loop of DjlJ This is because the amount of light is sufficiently small. [Effects of the Invention] As described above, according to the present invention, by first using an injection-locked semiconductor laser as a pumping light source, a high-gain rare earth element-doped glass waveguide amplifier can be realized. In addition, by using a feedback loop configuration for the pump light propagation waveguide, it is possible to increase the output of the injection-locked semiconductor laser and stabilize the oscillation wavelength, realizing a stable amplifier with high gain and little gain fluctuation. be able to. Furthermore, by using an elliptical glass waveguide with a planar structure to make the amplifier more compact, it is possible to expect smaller size, lower loss, and lower cost.

[Brief explanation of drawings]

1 to 6 show examples of the rare earth element-doped glass waveguide amplifier of the present invention, FIG. 1 is a side view of the first embodiment, and FIG. 2 is its n-II sectional view. , FIG. 3 is a side view of the second embodiment, FIG. 4 is a cross-sectional view along IV-IV thereof, FIG. 5 is a diagram showing the third embodiment, and FIG. 6 is a diagram showing the fourth embodiment. , FIG. 7 is a diagram schematically showing a conventional optical fiber amplifier.

Claims (1)

[Claims] 1. In a glass waveguide amplifier configured to couple pumping light from the input side of a rare earth element-doped glass waveguide through which signal light propagates, and extract the pumping light from the output side of the waveguide, A rare earth element-doped glass waveguide amplifier characterized in that an injection-locked semiconductor laser is used as the excitation light source. 2. The method according to claim 1, wherein the coupling of the excitation light to the rare earth element-doped glass waveguide and the extraction of the excitation light from the waveguide are performed by a resonator such as a ring resonator or a directional coupler. Rare earth element doped glass waveguide amplifier. 3. The rare earth element-doped glass waveguide amplifier according to claim 2, wherein the excitation light propagation path has a feedback loop configuration. 4. Claim 1, 2 or 3, wherein the injection-locked semiconductor laser is one with an amplifier function and is synchronized with the output light of a reference wavelength-stabilized semiconductor laser light source.
The rare earth element-doped glass waveguide amplifier described above. 5. The rare earth element doped glass waveguide amplifier according to claim 1, 2, 3 or 4, wherein the rare earth element doped glass waveguide amplifier is constructed of a planar structure glass waveguide. 6. The rare earth element doped glass waveguide according to claim 1, 2, 3 or 4, wherein the rare earth element doped glass waveguide and the excitation light coupling and extraction resonator are constructed of an optical fiber structure. Wavepath amplifier.