JPS6118935A - Generating method of visible light - Google Patents

Abstract

PURPOSE:To easily generate visible light of 0.3-1mum by making light pulses of a 1mum wavelength band incident on the fast axis of an optical fiber having birefringence and causing induced Raman scattering and 4 photon mixture and generating a sum frequency in the fiber. CONSTITUTION:Light pulses of high output from an exciting light source 1 are generated at intervals of, for example, 1-10ns as light pulses which have 200psec pulse width and 6kW peak power. The fast axis of polarization of the light pulses is made coincident with the fast axis of the birefringent optical fiber 4 by a polarizer 2 and the output of the polarizer 2 is made incident on the birefringent optical fiber 4 through a lens 3. Nonlinear optical effect, i.e. inductive Raman scattering and 4 photon mixing are caused in the optical fiber 4 to emit visible light (purple of 492nm, green of 514nm, and yellow of 538nm) from a lens 3'. Consequently, the visible light is generated with high efficiency.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a visible light generation method using an optical fiber, and in particular, to a method for generating visible light using an optical fiber, in particular, a method for producing stimulated Raman scattering and stimulated four-photon mixing by injecting a high-power optical pulse into the fast axis of a birefringent optical fiber. The present invention also relates to a method of highly efficiently obtaining light having a beam length of 0.3 to 1 μm by generating a sum frequency.

[Prior art]

In recent years, the application of light has expanded beyond the field of communications to the field of force measurement, making it possible to measure distances, speeds, and the number of revolutions per rotation. Furthermore, it is common to use light to measure the characteristics of optical fibers for communication. Under these circumstances, in order to expand the range of measurement targets and achieve highly accurate measurements, it is important to create a light source that can efficiently generate light of various wavelengths. In particular, there is currently no highly efficient light emitting method in the visible to ultraviolet range, and a highly efficient light source in this range is desired.

Incidentally, as a new light source, in recent years, studies have begun to consider generating light of a wavelength different from that of excitation light using nonlinear optical effects in optical fibers.

In this way, light sources using optical fibers have been attracting attention because they have the advantage of being able to efficiently couple with the optical fiber to be measured, especially when used to measure the characteristics of optical fibers. In one example of a light source, a true circular core fiber was used, and this fiber was connected to a 50 kW Q-switch Nd: YAG with a wavelength of 1.06 μm.
Furthermore, a mode-locked Q of 1100k is obtained by excitation with a laser to obtain light with a wavelength of 0.7 to 2.111m.
Switch Nd: It has also been reported that light with a wavelength of 0.3 to 2.1 μm can be obtained by exciting an optical fiber with a YAG laser.

However, these light sources have the disadvantage that the power conversion efficiency from the pumping light to the generated light is low.In addition, the power conversion efficiency is low, so in order to increase the output power, it is necessary to increase the input power. However, if the input power is too strong, the end face of the optical fiber will be burnt out. [Purpose] Therefore, the purpose of the present invention is to emit visible light using an optical fiber. An object of the present invention is to provide a visible light generation method that eliminates the above-mentioned drawbacks and can generate visible light easily and with high efficiency. In the present invention, the wavelength 1 μ
By using an m-band high-output light pulse using a birefringent optical fin and injecting the excitation light into the fast axis of its two principal axes, stimulated Raman scattering and four-photon mixing can occur in the optical fin. and the sum frequency is generated, and the wavelength is 0.3 to 1 μm.
of visible light with high efficiency.

Here, a plurality of visible wavelength lights can be generated simultaneously by inputting light into a plurality of birefringent optical fibers.

〔Example〕

The present invention will be described in detail below with reference to the drawings. One embodiment of the present invention is shown in FIG. 3 is a lens, and 4 is a birefringent optical fiber. For example, an optical pulse with a pulse width of 200 psec and a peak power of 6 kW is generated from the excitation light source 1 at an interval of 10 n5 ec, and the main axis of polarization of the optical pulse is aligned with the fast axis of the birefringent optical fiber 4 using the polarizer 2. After combining,
The polarizer output is passed through a lens 3 to a birefringent optical fiber 4.
Inject it into the A nonlinear optical effect occurs inside this birefringent optical fiber 4, and visible light is extracted from its output end via a lens 3'.

Here, an example of the spectrum of visible light coming out from the output end of the optical fiber 4 is shown in FIG. In this case, as shown in FIG. 2, the color is violet (wavelength: 430 nm).

Blue (492nm), green (5t4nm), yellow (538nm)
m) visible light is generated.

The dependence of these optical powers on the pumping light power is shown in FIG. As can be seen from this Figure 3, especially the wavelength λ" 514
Even if the excitation light power is several kilowatts, the nanometer light can provide a large power and can be sufficiently used as a light source. The power conversion efficiency from excitation light to visible light at this time is 0.5
~ 1 inch reed, compared to the conventional 0.1 inch, 5 to 10 inches
We were able to achieve double the conversion efficiency.

In the example shown in FIG. 1, the spectra of visible light generated when the main axis of polarization of the excitation light is incident on the fast axis of the birefringent optical fiber and when it is incident on the coupled axis are shown in FIGS. 4 (A) and (2), respectively. In the 0-stripe diagram 4 (g) shown in B), the solid line is the output from the fast axis, and the broken line is the output from the linked axis. In FIG. 4(B), the solid line is the output from the linked shaft, and the broken line is the output from the fast shaft. In order to achieve highly efficient conversion from excitation light to visible light, it is very important that the main axis of polarization of the excitation light coincides with the fast axis of the birefringent optical fiber. The wavelength of light changes depending on the type of birefringent optical fiber, so if two different types of birefringent optical fibers are connected, the types of wavelengths of light generated will also increase. That-
An example is shown in FIG. 5. In FIG. 5, the optical fiber 4 is
The optical fiber 5 is an optical fiber that generates light with a spectrum as shown in FIG. 2 (hl), and the optical fiber 5 is a fiber that generates light with a spectrum as shown in FIG. These two birefringent optical fibers 4 and 5 are cascade-connected at the fiber connection portion 5 so that their half axes coincide. When excitation light is incident on the fibers connected in this manner in the same manner as in FIG. 1, the visible light spectrum L emerging from the output end of the optical fiber 5 is as shown in FIG. 7. In this case, purple, blue, and green.

Yellow and orange (s64 nm) light is generated. Therefore, a sum output is obtained in which light of various wavelengths is spread from the optical fiber 5 and is generated from the two types of fibers 4 and 5, respectively. By connecting birefringent optical fibers, it is possible to obtain light of multiple required wavelengths at the same time.〇@8 Figure 8 shows a third embodiment of the present invention. In the embodiment, mirrors (laser mirrors) 7 and 7' that reflect only light with a specific wavelength λ are placed on the incident side of the lens and the output side of the lens 3, respectively, thereby oscillating light with a wavelength λ. [Effect] As explained above, according to the present invention, a high-output optical pulse is made to enter a birefringent optical fiber so that its plane of polarization coincides with the semi-axis. However, the use of a true circular fiber also has the advantage of being able to generate visible light with high efficiency.

Furthermore, when different types of birefringent optical fibers are connected so that their half axes coincide, light with the wavelengths of light that can be generated by each optical fiber is superimposed is generated. By connecting multiple types of birefringent optical fibers that can generate birefringent light, there is an advantage that the light can be obtained at the same time.

Furthermore, by placing mirrors at both ends of a birefringent optical fiber that reflect only a specific wavelength, it is possible to strongly oscillate light at that wavelength, which allows for sufficient output to be used as a light source. There are benefits to be gained.

Furthermore, since the light generated by the method of the present invention has a spot size close to the core diameter of the fiber, when used to measure the characteristics of an optical fiber for transmission, it is possible to By concentrating the light with a lens),
It is possible to couple the fiber under test with high efficiency.

[Brief explanation of the drawing]

Figure 1 is a diagram showing one embodiment of the present invention, Figure 2 is a spectrum diagram showing the spectrum of visible light generated from a birefringent optical fiber, and Figure 3 is a diagram showing the spectrum of visible light generated in the embodiment of Figure 1. Explanatory diagrams showing the dependence of power on the incident pumping light power, Figure 4 (6) and 忤) show the case where the main axis of polarization of the pumping light is incident on the semi-axis and transport of the birefringent optical fiber, respectively. A spectral diagram showing the spectrum of generated visible□ light, Fig. 5 Diagram showing another embodiment of the present invention in which different types of birefringent optical fibers are connected, Birefringent optical fiber in the example of Fig. 5 of the sixth circular Figure 7 is a spectrum diagram showing the spectrum of visible light obtained in the embodiment shown in Figure 5. Figure 8 is a spectrum diagram showing the spectrum of visible light generated by the embodiment shown in Figure 5. 01...-High power excitation light source, 2...Polarizer, 3.3...Lens, 4. ... Birefringent optical fiber, 5... Birefringent optical fiber 1

Claims (1)

[Claims] 1) A light pulse with a wavelength of 1 μm is incident on the fast axis of a birefringent optical fiber having birefringence to generate stimulated Raman scattering, four-photon mixing, and a sum frequency in the optical fiber. A visible light generation method characterized by obtaining light with a wavelength of 0.3 to 1 μm from the optical fiber. 2) In the method for generating visible light according to claim 1, the birefringent optical fiber is formed by cascading a plurality of birefringent optical fibers that generate visible light of different wavelengths, and A visible light generation method characterized by simultaneously obtaining visible light outputs of multiple wavelengths from a refractive optical fiber.