JPH1012956A - Semiconductor laser pumping solid laser oscillation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an oscillation method for solid laser in which a laser rod has high energy storage efficiency. SOLUTION: A modulator 8 received a current from a power supply 9 and produce a saw-tooth driving current represented by a function t(x)=x which is fed to a semiconductor laser 1. Since the semiconductor laser 1 delivers a pumping light 3 to a laser rod 2 provided in each laser resonator 5, 6 together with a Q switch 4 and the modulator 8 outputs a driving current being represented by a function f(x) =x.e<x-1> , energy storage efficiency of the laser rod 2 can be enhanced. Consequently, the oscillation efficiency of laser can be enhanced while reducing the size and the power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser pumped solid-state laser oscillation method.

[0002]

2. Description of the Related Art A conventional semiconductor laser pumped solid-state laser that oscillates a giant pulse using a Q switch will be described with reference to FIG. In FIG. 3, a semiconductor laser device 01 for excitation is connected to a power supply 9 via a modulator 08, and an excitation light 03 is incident on the laser rod 2.

On the other hand, a rear mirror 5 and a front mirror 6 having a laser rod 2 and a Q switch
Are adjusted so that their central axes coincide, and constitute a laser resonator. The rear mirror 5 is totally reflected by the laser beam, and the front mirror 6 is coated so as to transmit the laser beam slightly (1 to 10%).

[0004] In the laser rod 2, ions (usually neodymium or chromium) of a laser medium doped therein are pumped by an excitation light 03 emitted by a semiconductor laser device 01.
Is excited to a level higher than the ground state.

The Q switch element 4 functions as an optical shutter for rapidly changing the Q value of the optical resonator with a solid-state laser and extracting a pulse having a large peak output.
After the ions in the laser rod 2 are sufficiently excited to the upper level, when they are opened, the rear mirror 5 and the front mirror 6 are opened.
The laser amplifying action due to the stimulated emission occurs suddenly between the laser beams, and the laser light is oscillated to emit the pulsed high-power light 7.

The pulse laser using the Q-switch element 4 has an output per unit time of 10 ³ to 10 ⁵ times that of a continuous wave laser without the Q-switch element 4, so that it can be used for processing, measurement, etc. Widely used for

The state of ions in the laser rod 2 will be described with reference to FIG. FIG. 4A shows a time waveform of a current of the modulator 08 for driving the semiconductor laser device 01 for excitation, which is generally a rectangular wave. Normal,
Lifetime τ _F of laser medium ions (represents the time from the upper level to the spontaneous return to the ground state, defined as the time for 1 / e 全体 37% of the total number to return to the ground state. Neodymium ions In this case, the excitation is constant for about 250 μs).

FIG. 4B shows the temporal change in the number of ions at the upper level in the laser rod 2. When the laser is excited with a constant excitation power as shown in the waveform of FIG. The number of ions at the upper level increases linearly with time, but gradually decreases.

This is because the spontaneous emission of ions causes the previously excited ions to return to the ground state spontaneously. This spontaneous emission of ions does not contribute to laser oscillation at all. Normally, the Q switch element 4 is turned on as shown in FIG. 4C after the elapse of the time τ _F from the start of the excitation, and the pulse laser light as shown in FIG. 4D is oscillated.

[0010]

As described above, the peak output (output per unit time) of a conventional semiconductor laser-pumped solid-state laser using a Q-switch element is several times.
Since it is very large, from KW to several MW, it is widely used for processing and measurement, but it is useless from the viewpoint of energy storage efficiency (energy that contributed to laser oscillation / excitation energy injected into the laser rod). There was a part.

FIG. 4 (b) shows how this useless portion occurs.
As shown in (1), spontaneous emission of previously excited ions occurs during excitation, which leads to wasteful energy emission. Since the energy storage efficiency of the laser rod 2 directly affects the laser oscillation efficiency (laser output / laser driving power), it is necessary to approach 1 as much as possible.

Here, the temporal change of the drive current supplied to the semiconductor laser device for excitation is represented by a function f (x), and x
Is the time standardized by the lifetime τ _F , the energy storage efficiency η _ST until x = 1, that is, t = τ _F is expressed by the following equation.

[0013]

(Equation 1)

FIG. 5 illustrates this, and η _ST is represented by the ratio of the area of the square to the area of the hatched portion in FIG. That is, only the shaded portion contributes to laser oscillation, the stored energy efficiency is 63%, and 37% is wasted, and improvement thereof has been desired. The present invention seeks to solve the above problems.

[0015]

[Means for Solving the Problems]

(1) A semiconductor laser pumped solid-state laser oscillation method according to the first aspect of the present invention, wherein a Q-switch element and a laser rod are provided in a laser resonator, and a current is input from a power supply via a modulator. In a semiconductor laser-pumped solid-state laser in which a pumping light is incident on the laser rod, a modulator to which a current is input from a power supply outputs a sawtooth-shaped drive current represented by a function f (x) = x, and this drive current Is input to the laser rod, and the laser resonator outputs giant pulse laser light.

In the above, the variable x of the function f (x) is a time standardized by the life of the laser medium ions in the laser rod, and is a ratio of the energy contributing to laser oscillation to the excitation energy injected into the laser rod. The energy storage efficiency η _ST of the laser rod expressed by the ratio can be expressed by the following equation (1).

[0017]

(Equation 2)

In the case of the present invention, the driving current output from the modulator is represented by a function f (x) = x.
The energy is converted into the following equation (2), and the energy storage efficiency of the laser rod can be obtained from the equation (2).

[0019]

(Equation 3)

In the present invention, as described above, the energy storage efficiency of the laser rod is 0.72, which is 14% higher than the conventional case of 0.63, and the energy loss due to spontaneous emission of ions is reduced. Thus, the laser oscillation efficiency can be improved.

(2) According to a second aspect of the present invention, in the semiconductor laser-excited solid-state laser oscillation method according to the first aspect, the driving current output from the modulator is a function f (x) = x ·
The drive current is characterized by a saw-tooth waveform drive current represented by ^{ex- 1} .

In the present invention, since the driving current output from the modulator is represented by the function f (x) = x · ex ⁻¹ , the energy storage efficiency η _ST of the laser rod is given by the following equation (3). And can be obtained from this equation (3).

[0023]

(Equation 4)

In the case of the present invention, the energy storage efficiency of the laser rod is 0.77 as described above, and the above-mentioned invention (1)
In this case, the laser oscillation efficiency can be further improved as compared with the case (1).

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor laser pumped solid-state laser according to one embodiment of the present invention will be described with reference to FIG.

The present embodiment shown in FIG. 1 is a semiconductor laser pumped solid-state laser in which a Q switch element 4 and a laser rod 2 are provided between a rear mirror 5 and a front mirror 6 forming a laser resonator, and is connected to a power supply 9. Modulator 8 that outputs a drive current having a saw-tooth waveform, and modulator 8
A semiconductor laser device 1 is provided which receives a drive current having a more sawtooth waveform, generates excitation light 3 and enters the laser rod 2. The operation of the devices other than the semiconductor laser device 1 and the modulator 8 is the same as that of the conventional device, and a detailed description thereof will be omitted.

In this embodiment, since the driving current output from the modulator 8 has a sawtooth waveform, this driving current can be represented by a function f (x) = x, and the energy contributing to laser oscillation and Energy storage efficiency η of laser rod 2 represented by the ratio of excitation energy injected into laser rod 2
_ST can be obtained by the following equation (2).

[0028]

(Equation 5)

FIG. 2 illustrates the above, and the excitation energy injected into the laser rod 2 and the energy contributing to laser oscillation correspond to the area of the triangle and the area of the hatched portion, respectively. The area ratio of the latter to the former represents the energy storage efficiency η _ST .

In the case of this embodiment, the energy of the laser rod 2 is
Lugi accumulation efficiency η_STIs 0.72, which is
1.14 times the energy storage effect compared to 0.63
Rate η _STWas improved by 14%.

A semiconductor laser-pumped solid-state laser according to another embodiment of the present invention will be described. In the present embodiment, the drive current input to the semiconductor laser device by the modulator can be represented by a function f (x) = x · ex ^-1 .
The energy storage efficiency η _ST of the laser rod can be obtained by the following equation (3).

[0032]

(Equation 6)

In the case of the present embodiment, the energy storage efficiency η _ST is 0.77, and the energy storage efficiency of the laser rod can be further improved as compared with the case of the one embodiment.

[0034]

According to the semiconductor laser-excited solid-state laser oscillation method of the present invention, a modulator to which a current is input from a power supply outputs a drive current having a saw-tooth waveform represented by a function f (x) = x. And the semiconductor laser device inputs excitation light to a laser rod provided together with a Q switch element in a laser resonator,
By setting the drive current output from the modulator to be represented by the function f (x) = x · ex ⁻¹ , the energy storage efficiency of the laser rod can be improved as compared with the conventional one, and the laser oscillation efficiency can be improved. It is possible to reduce the size of the device and reduce the amount of power consumption.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a semiconductor laser-pumped solid-state laser according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the energy storage efficiency of the laser rod according to the embodiment.

FIG. 3 is an explanatory view of a conventional device.

FIG. 4 is an operation explanatory view of a conventional device.

FIG. 5 is an explanatory diagram of energy storage efficiency of a laser rod of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser device 2 Laser rod 3 Excitation light 4 Q switch element 5 Rear mirror 6 Front mirror 8 Modulator 9 Power supply

[Procedure amendment]

[Submission date] July 16, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

Claims (2)

[Claims] 1. A semiconductor laser-pumped solid-state laser in which a Q-switch element and a laser rod are provided in a laser resonator, and a semiconductor laser device to which a current is input from a power supply via a modulator enters pump light into the laser rod. In the above, the modulator to which a current is input from the power supply outputs a drive current having a sawtooth waveform represented by a function f (x) = x, and the semiconductor laser device to which the drive current is input generates excitation light to generate a laser beam. A semiconductor laser-excited solid-state laser oscillation method, wherein the laser cavity emits a giant pulse laser beam upon incidence. 2. The semiconductor laser-excited solid-state laser oscillation method according to claim 1, wherein the driving current output from the modulator is a driving current having a sawtooth waveform represented by a function f (x) = x · ex ^−1. A solid-state laser oscillation method excited by a semiconductor laser.