JPS6019679B2 - Laser oscillation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to, for example, a light source of an optical communication system,
This invention relates to a laser oscillation device using a laser medium such as a semiconductor or gas, and is intended to easily obtain optical power of multiple wavelengths, especially at long wavelengths.

In today's optical communications trends, lasers are used as light sources for communications, and optical fibers are used as transmission media. The optical fiber is provided outside the laser resonator separately from the laser. There are reports on fiber ramasor lasers that pump optical fibers with Nd30:YAG lasers and lasers using Nd-containing fibers, but these differ greatly from this invention in that the fibers are not used as waveguides in the laser resonator. ing. In the past, lasers with a resonator length of a few hundredths of a meter have been manufactured, but due to diffraction loss, propagation loss, etc., no one with a resonant wavelength of several hundred lengths has been produced until now.

This invention is characterized by inserting a single-mode optical fiber into a laser resonator to lengthen the resonator length to cause laser oscillation.The purpose of this invention is to realize a new oscillation wavelength by the nonlinear optical effect in the optical fiber The aim is to realize a long-distance single-mode output laser and a long-distance direct communication system using the relay section as a laser resonator. The drawings will be explained in detail below. FIG. 1 shows an embodiment of the present invention, in which laser mirrors 11, 12 and objective lenses 15, 16, 3 are optical fibers, and in addition to a plasma laser tube as a population inversion medium 13 for laser oscillation, an optical fiber 14 is used in this invention. is inserted to lengthen the resonator length. An objective lens 15 is provided between each end of the optical fiber 14 and the mirror 12 and the soot material 13.
, 16 are inserted. The population inversion gain of the soot material 13 is made sufficiently larger than the linear loss of the optical fiber 14 and the objective lenses 15 and 16 system. Let the reflectance of the mirrors 11 and 12 at both ends be r, , [2, the gain per unit length of the population inversion medium 13 be g (1/m), and the loss per unit length of the optical fiber 14 be Q (1/m). /m), and the loss due to the objective lenses 15 and 16 system is R.

Here, the length of the population inversion soot material 13 is 1, and the length of the optical fiber 1 is
Assuming that the length of 4 is 12, the oscillation conditions of the laser device shown in FIG. 1 are given as follows. r, r2R2e2(9
, -Q12)≧1 '1'' Solving equation 11 for 12 yields the allowable fiber length, resulting in the following equation.

l2s nose, - (ln point + ln Australia) '21 For example, considering a wavelength of 1.15 mm m ratio -Ne laser, the population inversion gain is about 2 harmonics/m.

r, , r2 are both 0.95, R is 0.6, and the loss of the optical fiber at a wavelength of 1.15 mm is 0.95. It is assumed that the length of the population inversion soot material 13 of the parent/object laser is 2h. In this case, Q = 1.382 x 10-4 (11 m), g = 4.6
1×10-1 (1/m), vine (ln point + ln) = -4
・60XI. -1, so 12S3.34×1pi(
m) becomes '3'.

Therefore, even if about three optical fibers 14 are inserted into the laser resonator, sufficient oscillation can be achieved in the case of a He-Ne laser under the above conditions. At this time, the longitudinal mode interval Δf of laser oscillation is given by the following equation.

Δf=base=3femaleHZ ■ However, n indicates the refractive index of the core portion of the optical fiber 14.

On the other hand, the gain bandwidth of the 1.15 French mHe-Ne laser is determined by the Doppler width, and is approximately 80 MHz. Therefore, the number of longitudinal mode spectra that can be oscillated is approximately 23.
．． It will be 3 x 1 book. Since the number of longitudinal mode spectra is large in this way, and when the optical fiber is long, the nonlinear pull-in effect of the laser soot acts a lot, and single mode oscillation is possible. When the optical fiber 14 is provided outside the resonator, there is no such pull-in effect, and the optical fiber 14 is omitted to increase the free space length and the mirrors 11 and 12
Even if the interval is made longer, no pulling effect will be obtained, and if the length in free space is made longer, the loss will be large, so it cannot be made as long as the left. FIG. 2 shows a case in which a N:YAG rod for a solid-state laser with a wavelength of 1.06 fm is equipped as the population inversion host 13 for laser oscillation instead of the plasma laser tube shown in FIG.

The single-line gain of a solid-state laser is approximately 1 larger than the cost of the old gas medium due to its density. Here, if 5 skin YAG rods are used, the gain will be 5 MB. Among the above conditions, if r, , r2R are the same and Q is 1 lull/k, then
Obtain the following optical fiber allowable insertion length. 12S4886
×1 pi(m) [5'If laser oscillation is realized with such a length, one communication relay section can be configured as one laser resonator.

When using single mode fiber, the coupling efficiency R=
Even if it is 0.1 (1 melon B), the maximum is 3 in the case of YAG laser.
9. It oscillates overboard.

At this time, if the core diameter of the optical fiber 14 is set to 5 to loAm, the optical field density in the core becomes very high, and nonlinear optical effects enable oscillation in a long wavelength region and generation of optical harmonics. In this case, stimulated Raman scattering in optical fibers is used. In other words, when using a low-loss single mode fiber with a length of 300 to 500 mm, the optical intensity at the fiber core will be 2 to 50 mm.
When the power reaches about 3 W, conducive Raman scattering occurs in the fiber and light amplification occurs. When the gain of the resonator becomes larger than its loss, oscillation occurs at a new wavelength due to conducive Raman scattering, similar to the theory described above. For example, in the case of Nd30:YAG laser, the original oscillation line is 1.06 m,
The oscillation line of stimulated Raman is 1.1 for silica fiber.
Occurs around 2m wide. Since it is a laser oscillation, the Raman output is continuous light, and the output is also large. In the case of a 3 skin h resonator, the Raman output is 3 for a 1.06 m optical output.
It becomes 0% or more.

This multi-wavelength light source has the advantage of providing stable continuous light, unlike the conventional Raman scattering in fibers caused by powerful pulsed laser beams. FIG. 3 shows a resonator, that is, a mirror 11,
This is a configuration example in which an intensity modulation element 17 using phase modulation using a piezoelectric effect or Farade rotation is attached to a part of the optical fiber 14 between the optical fibers 12.

Here, the modulation element 17 and the modulator driver 18 are driven. With this configuration, efficient phase or intensity modulation can be achieved with a small modulation voltage or current. Furthermore, the third
In the figure, the modulation element 17 is attached to a part of the optical fiber 14, but similar modulation can be performed by placing the modulation element 17 at any position between the mirrors 11 and 12. In this case, a modulation element using an electro-optic effect or an acousto-optic effect can also be used. If dozens of optical fibers 14 are inserted into the laser resonator and this is used as a transmission line, a long-distance non-repeater transmission system can be realized by using the modulator driver I8 as the transmitter and the photodetector 19 as the receiver. It can be achieved.
As explained above, this invention uses several to dozens of optical fibers to achieve high output longitudinal single mode, generation of new oscillation wavelengths, and long-distance direct communication system in which one relay section is used as a laser oscillator. There are many advantages.

Furthermore, the vertical single mode has the advantage of allowing heterodyne communication using optical phase information. Furthermore, by using a single mode optical fiber, optical harmonics can be generated due to the nonlinear optical effect in the single mode optical fiber.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example in which the present invention is applied to a -N6 laser with a wavelength of 1.15 m, and Fig. 2 shows an example in which the invention is applied to a -N6 laser with a wavelength of 1.15 m.
06〃Block diagram showing an example implemented in mYAG laser, Part 3
The figure is a configuration diagram showing an example in which an optical modulator is added to the device of the present invention. 11, 12: Laser mirror, 13: Laser population inversion soot, 14: Optical fiber, 15, 16: Objective lens, 17
: Modulation element, 18: Modulator driver, 19: Photodetector. O figure outside figure 2 figure soup 3 figure

Claims (1)

[Claims] 1 Laser oscillation characterized in that a population inversion medium for laser oscillation and a single mode optical fiber are installed inside a set of laser mirrors, and these are optically coupled via a lens to form an optical resonator. Device.