JPH0943652A - Laser oscillator and laser light source driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser oscillator and a laser light source driving method especially provided with a nonlinear optical medium for generating a second harmonic wave and also capable of pulse-driving the light source with a high efficiency, with respect to a laser oscillator and a laser light source driving method using a semiconductor laser, etc. SOLUTION: An optical resonator is composed of a laser crystal 300 and an output mirror 500, and a nonlinear optical medium 400 is inserted in the optical resonator to generate a second harmonic wave, and it is also possible for the optical resonator to be pumped with the laser light source 100 and to make a driving pulse period T of a pulse driving means to be τFL>T-τ to τFL (fluorescentlife). Also, it is possible to make a first pulse drive the laser light source 100 up to a degree of not emitting light yet but make a second pulse drive the laser light source 100 to emit light. But τ means a pulse width here.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser oscillating device using a semiconductor laser and the like and a laser light source driving method, and in particular, it includes a non-linear optical medium for generating a second harmonic wave, The present invention relates to a laser oscillating device and a laser light source driving method capable of efficiently pulse driving.

[0002]

2. Description of the Related Art Conventionally, a laser oscillation device using a semiconductor laser has existed and has been applied to various fields.

[0003] In recent years, due to the dramatic progress in laser technology, not only laser oscillators using commercial power supplies,
Like a surveying instrument, a laser oscillation device used outdoors by battery driving is also frequently used.

[0004]

However, the laser oscillating device driven by the battery has a problem that it consumes a relatively large amount of power and the operating time tends to be limited.

Therefore, there has been a strong demand for the appearance of a laser oscillation device capable of oscillating a laser beam with high efficiency, reducing the power consumption, and dramatically increasing the continuous use time.

[0006]

The present invention has been devised in view of the above problems, and an optical resonator comprising at least a laser crystal and an output mirror, and a laser light source for pumping the optical resonator. And a pulse driving means for driving the laser light source, which is a period T of a driving pulse of the pulse driving means.
But with respect to tau _FL (fluorescence lifetime), and has a tau _FL> T over tau. (However, τ is the pulse width)

The present invention also provides an optical resonator comprising at least a laser crystal and an output mirror, a non-linear optical medium inserted into the optical resonator for generating a second harmonic, and the optical resonator. A laser oscillating device comprising a laser light source for pumping with respect to the laser light source and a pulse driving means for driving the laser light source, wherein a period T of a driving pulse of the pulse driving means is τ _FL (fluorescence lifetime). On the other hand, τ _FL > T−τ can be set.

Then, the pulse driving means of the present invention comprises a pair of two pulses, a first pulse and a second pulse,
It is configured to drive the laser light source, and the first pulse drives the laser light source to such an extent that the laser light source does not emit light, and the second pulse drives the laser light source to emit light. It can also be configured.

Further, the laser light source driving method of the present invention is a driving method of performing pulse driving in order to drive a laser light source for pumping, with respect to an optical resonator including at least a laser crystal and an output mirror. , The driving pulse period T is τ _FL > T with respect to τ _FL (fluorescence lifetime)
-Tau. (However, τ is the pulse width)

The laser light source driving method of the present invention comprises:
A driving method in which pulse driving is performed to drive a laser light source for pumping with respect to an optical resonator including at least a laser crystal including a nonlinear optical medium for generating a second harmonic and an output mirror. a is the period T of the driving pulse with respect to tau _FL (fluorescence lifetime), tau _FL
It is also possible to make> T−τ.

The driving pulse of the method for driving a laser light source of the present invention is such that the laser light source is driven with two pulses of a first pulse and a second pulse as one set. The first pulse may be driven so that the laser light source does not emit light, and the second pulse may be driven so that the laser light source emits light.

The laser oscillating device of the present invention comprises an optical resonator comprising at least a laser crystal and an output mirror, a laser light source for pumping the optical resonator, and a pulse for driving the laser light source. In the laser oscillation device including a driving unit, the driving pulse of the pulse driving unit has a pulse width capable of obtaining at least a first pulse.

Further, the laser oscillating device of the present invention comprises an optical resonator comprising at least a laser crystal and an output mirror,
A laser oscillating device comprising a laser light source for pumping to the optical resonator and a pulse driving means for driving the laser light source, wherein at least a first pulse can be obtained as a driving pulse of the pulse driving means. It is a pulse width, and the period T of the driving pulse of the pulse driving means is configured so that τ _FL > T−τ with respect to τ _FL (fluorescence lifetime).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention constructed as described above
An optical resonator is formed from at least a laser crystal and an output mirror, a laser light source pumps with respect to the optical resonator, and a pulse driving means drives the laser light source. The period T of
_{For FL} (fluorescence lifetime), τ _FL > T−τ.
(However, τ is the pulse width)

According to the present invention, an optical resonator is formed from at least a laser crystal and an output mirror, and a nonlinear optical medium for generating a second harmonic is inserted into the optical resonator,
The laser light source pumps to the optical resonator, and the driving pulse period T of the pulse driving means is τ _FL (fluorescence lifetime)
On the other hand, τ _FL > T−τ can be set.

Then, the pulse driving means of the present invention comprises a pair of two pulses, a first pulse and a second pulse,
It is designed to drive the laser light source, and the first pulse drives the laser light source to the extent that it does not emit light, and the second pulse
Pulse can also be driven to emit a laser light source.

Further, according to the laser light source driving method of the present invention, in order to drive the laser light source for pumping with respect to the optical resonator including at least the laser crystal and the output mirror, the period T of the driving pulse is τ _FL. Pulse driving can be performed so that τ _FL > T−τ with respect to (fluorescence lifetime). (However, τ is the pulse width)

The laser light source driving method of the present invention is
In order to drive the laser light source for pumping with respect to the optical resonator including at least the laser crystal and the output mirror containing the nonlinear optical medium for generating the second harmonic, the period T of the drive pulse is , Τ _FL (fluorescence lifetime), pulse driving can be performed so that τ _FL > T−τ.

The driving pulse of the method for driving a laser light source of the present invention is such that the laser light source is driven by using two pulses of the first pulse and the second pulse as one set. The pulse can drive the laser light source to the extent that it does not emit light, and the second pulse can drive the laser light source to emit light.

In the laser oscillator of the present invention, an optical resonator is formed from at least a laser crystal and an output mirror, and a laser light source pumps the optical resonator,
The pulse driving means drives the laser light source, and the driving pulse of the pulse driving means has a pulse width capable of obtaining at least a first pulse.

Further, in the laser oscillator of the present invention, an optical resonator is formed from at least a laser crystal and an output mirror, and a laser light source pumps the optical resonator,
The pulse driving means drives the laser light source, the driving pulse of the pulse driving means has a pulse width that can obtain at least a first pulse, and the cycle T of the driving pulse of the pulse driving means is τ _FL ( Pulse driving can be performed so that τ _FL > T−τ for the fluorescence lifetime).

[0022]

【Example】

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a laser oscillator 10 of this embodiment.
00, a laser light source 100, a condenser lens 200, a laser crystal 300, and a nonlinear optical medium 40.
0, an output mirror 500, and a laser driving means 600.

The laser light source 100 is for generating laser light, and a semiconductor laser is used in this embodiment. In this embodiment, the laser light source 100
Has a function as a pump light generator for generating a fundamental wave. The laser light source 100 is not limited to the semiconductor laser, but may be any laser light that can generate laser light.
Any light source means can be adopted. The laser driving means 600 is for driving the laser light source 100, and in this embodiment, the laser light source 100 is used.
Can be pulse driven.

The laser crystal 300 is a medium having a negative temperature and is used for amplifying light. For this laser crystal 300, YAG (yttrium aluminum garnet) doped with Nd ³⁺ ions or the like is adopted. YAG is 946 nm, 1064 nm, 1319n
It has an oscillation line such as m.

The laser crystal 300 is not limited to YAG, and the oscillation line is 1064 nm (Nd: YVO ₄ ), or the oscillation line is 700 to 900 nm (Ti: Sapphir).
e) etc. can be used.

Laser light source 100 of laser crystal 300
On the side, a first dielectric reflection film 310 is formed.
The first dielectric reflection film 310 is used for the laser light source 100.
Is highly transmissive to SHG (SECO) and is highly reflective to the oscillation wavelength of the laser crystal 300.
It is also highly reflective against ND HARMONIC GENERATION.

The output mirror 500 is constructed so as to face the laser crystal 300 on which the first dielectric reflection film 310 is formed, and the laser crystal 30 of the output mirror 500 is arranged.
The 0 side is processed into a shape of a concave spherical boundary having an appropriate radius, and a second dielectric reflection film 510 is formed. The second dielectric reflection film 510 is formed by the laser crystal 3
Highly reflective to the oscillation wavelength of 00, and SHG (SEC
It is highly transparent to OND HARMONIC GENERATION.

As described above, by combining the first dielectric reflecting film 310 of the laser crystal 300 and the output mirror 500, the light flux from the laser light source 100 is condensed by the condensing lens 200.
When the laser crystal 300 is pumped through the light, the light reciprocates between the first dielectric reflection film 310 of the laser crystal 300 and the output mirror 500, and the light can be confined for a long time. Can be amplified.

In this embodiment, the first crystal of the laser crystal 300 is used.
The nonlinear optical medium 400 is inserted in the optical resonator composed of the dielectric reflection film 310 and the output mirror 500.

Now, the nonlinear optical effect will be briefly described.

When an electric field is applied to a substance, electric polarization occurs.
When this electric field is small, the polarization is proportional to the electric field,
In the case of strong coherent light such as laser light, the proportional relationship between the electric field and the polarization is broken, and a nonlinear polarization component proportional to the square and the third power of the electric field becomes dominant.

Therefore, in the nonlinear optical medium 400, the polarization generated by the light wave includes a component proportional to the square of the electric field of the light wave.
Coupling occurs between light waves of different frequencies, generating harmonics that double the light frequency. This second harmonic generation (SH
G) is SECOND HARMONIC GENER
It is called ATION.

In this embodiment, the nonlinear optical medium 400 is
It is called an internal type SHG because it is inserted in the optical resonator composed of the laser crystal 300 and the output mirror 500, and the converted output is proportional to the square of the fundamental wave optical power. There is an effect that the large light intensity inside can be directly used.

The nonlinear optical medium 400 is, for example, KTP.
(KTiOPO ₄ potassium titanyl phosphate) and BBO
(Β-BaB ₂ O ₄ β-type lithium borate), LBO (L
iB ₃ O ₅ lithium triborate) etc. are used, and mainly
It is converted from 1064 nm to 532 nm.

Further, KNbO ₃ (potassium niobate) or the like is also adopted, and mainly converted from 946 nm to 473 nm.

In FIG. 1, ω is the angular frequency of the optical fundamental wave, and 2ω is the second harmonic (SHG).

Next, some consideration will be given to the driving of the laser oscillator 1000.

FIG. 2 shows the relationship between the population inversion and the light intensity during relaxation oscillation of a general laser light source. FIG.
The delta N (t) shown therein indicates the population inversion (gain), φ (t) indicates the light intensity, and the horizontal axis indicates the passage of time.

It is understood from FIG. 2 that the first spike (that is, the first pulse) rises when the population inversion reaches the maximum, and the maximum light intensity occurs.

Further, FIGS. 3 (a), 3 (b) and 3 (c)
3A is a schematic diagram showing a gain switch, and FIG.
FIG. 3 is a diagram showing a relationship between time and excitation intensity, and FIG.
[Fig. 3] is a diagram showing a relationship between time and light intensity, and Fig. 3 (c) is a diagram showing a relationship between time and population inversion.

By observing these figures, it is understood that the maximum light intensity occurs after a certain excitation time.

Next, FIG. 4 shows the relationship between the population inversion and the light intensity in FIG. 2 separately. If continuous wave drive power is supplied to the semiconductor laser, the maximum light intensity is generated in response to the first pulse, and then,
Since the light intensity decreases and converges to a constant light intensity, the light extraction is most efficient if only the first pulse is used.

Further, referring to FIGS. 5 (a) and 5 (b), the case where the continuous pulse drive power is supplied to the semiconductor laser will be described.

The drive pulse for driving the semiconductor laser and the optical pulse output from the semiconductor laser have substantially the same period and pulse width.

FIG. 5A shows the case where the period T of the continuous pulse supplied to the semiconductor laser has a relationship of τ _FL <T-τ. Where τ _FL is the fluorescence lifetime and τ is the pulse width.

On the other hand, in FIG. 5B, the period T of the continuous pulse supplied to the semiconductor laser is τ _FL > T−τ.
This is the case for the relationship.

As shown in FIG. 5 (b), by applying the next pulse to the semiconductor laser during τ _FL (fluorescence lifetime), a new population inversion is added to the remaining population inversion, and the effective maximum is obtained. It is understood that only light having a light intensity of can be continuously generated.

Next, the relationship between the output of the semiconductor laser and the output when the nonlinear optical medium 400 is inserted will be described with reference to FIGS. 6 (a) to 6 (d).

FIG. 6A shows the relationship between the current consumption of the semiconductor laser and the output of the semiconductor laser.
After the offset current, there is a linear relationship.

FIG. 6B shows the output of the semiconductor laser and
It shows the relationship with the output of the optical fundamental wave in the optical resonator, and has a linear relationship after the offset.

FIG. 6 (c) shows the relationship between the output of the optical fundamental wave in the optical resonator and the output of the second harmonic (SHG) when the nonlinear optical medium 400 is inserted. It is understood that the harmonic (SHG) output is proportional to the square after the offset of the output of the optical fundamental wave in the optical resonator.

Therefore, the current consumption of the semiconductor laser and the second
The relationship with the harmonic (SHG) output is proportional to the square as shown in FIG. 6 (d).

Therefore, the nonlinear optical medium 40 is placed in the optical resonator.
If 0 is inserted and the laser driving means 600 drives the semiconductor laser of the laser light source 100 so that the next driving pulse is applied within τ _FL (fluorescence lifetime), as shown in FIG. The laser can be oscillated.

That is, FIG. 7 shows that when the semiconductor laser of the laser light source 100 is driven by the pulse width τ, the pulse peak current I _P , and the pulse period T, the laser light having the optical pulse width τ ′ and the optical pulse peak output P ^P _SH is generated. Will occur.

The average current flowing through the semiconductor laser at this time is I _av , and the average output of the light pulse is P ^av _SH .

When the laser driving means 600 continuously drives the laser light source 100 (provided that the same continuous output P ^cw _SH as the average pulse output P ^av _SH is generated), the continuous operating current I _CW of Since the size is required, the current of I _CW -I _av can be saved when the laser light having the same output as the continuous wave is generated by the pulse driving.

Further, in the case of pulse driving, since the operation is intermittent, the average value will be compared with the continuous operation. The average pulse current I _av next to the case of pulse drive, smaller than a continuous operation current I _CW.

Therefore, when a laser beam having the same output as a continuous wave is generated by pulse driving, I _CW -I _av
The effect is that the current can be saved.

In this embodiment, the laser light source 100 is driven by intermittently supplying one pulse, but it is also possible to drive the laser light source 100 with two or more pulses as one set. it can.

For example, the pulse driving means 600 is configured to drive the laser light source 100 by using two pulses of the first pulse and the second pulse as one set, and the first pulse is the laser light source 100. Can be driven so as not to emit light, and the second pulse can drive the laser light source 100 to emit light.

As described above, if the laser light source 100 is driven with two or more pulses as one set, the light emission time can be shortened, and the laser light source 100 can have a long life.

Since the laser oscillation device 1000 has a characteristic that when light emission is driven, it stabilizes to a constant light emission through relaxation oscillation after peak light emission. When the intensity is set to be the same as that of continuous light emission, light emission driving with lower power consumption can be performed as compared with continuous light emission.

[0065]

According to the present invention configured as described above, an optical resonator comprising at least a laser crystal and an output mirror, a laser light source for pumping the optical resonator,
A laser oscillating device comprising pulse driving means for driving the laser light source, wherein a period T of a driving pulse of the pulse driving means is τ _FL (fluorescence lifetime),
Since τ _FL > T−τ, there is an effect that the optical resonator can be pumped by the laser light having the maximum light intensity by the first pulse, and the laser light can be oscillated with high efficiency.

The present invention also provides an optical resonator comprising at least a laser crystal and an output mirror, a non-linear optical medium inserted into this optical resonator for generating a second harmonic, and the optical resonator. A laser oscillating device comprising a laser light source for pumping to said and a pulse drive means for driving this laser light source, wherein the period T of the drive pulse of said pulse drive means is τ _FL (fluorescence lifetime)
On the other hand, since τ _FL > T−τ, a strong second harmonic can be generated in proportion to the square of the output of the semiconductor laser, and the laser light is oscillated with extremely high efficiency. Therefore, there is an outstanding effect that the current consumption can be reduced and energy saving can be realized.

Further, the pulse driving means of the present invention is configured to drive the laser light source with two pulses of the first pulse and the second pulse as one set, and the first pulse. Is driven so that the laser light source does not emit light, and the second pulse is driven so that the laser light source emits light, so that the light emission time can be shortened and the laser light source has a long life. The effect is that you can.

[0068]

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a laser oscillation device 1000 according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between population inversion and light intensity during relaxation oscillation of a semiconductor laser.

FIG. 3 (a) is a schematic diagram showing a gain switch, showing a relationship between time and excitation intensity.

FIG. 3B is a schematic diagram showing a gain switch, showing the relationship between time and light intensity.

FIG. 3C is a schematic diagram showing a gain switch, showing a relationship between time and population inversion.

FIG. 4 is a diagram showing a relationship between population inversion and light intensity.

FIG. 5A is a diagram illustrating a case where the cycle T of the continuous pulse supplied to the semiconductor laser has a relationship of τ _FL <T−τ.

FIG. 5B is a diagram illustrating a case where the period T of the continuous pulse supplied to the semiconductor laser has a relationship of τ _FL > T−τ.

FIG. 6A is a diagram showing the relationship between the current consumption of the semiconductor laser and the output of the semiconductor laser.

FIG. 6B is a diagram showing the relationship between the output of the semiconductor laser and the output of the optical fundamental wave in the optical resonator.

FIG. 6C shows the output of the optical fundamental wave in the optical resonator and the second harmonic (SH) when the nonlinear optical medium 400 is inserted.
It is a figure which shows the relationship with G) output.

FIG. 6D is a diagram showing the relationship between the current consumption of the semiconductor laser and the second harmonic (SHG) output.

FIG. 7 is a diagram comparing a case where the laser oscillator 1000 is continuously driven and a case where the laser oscillator 1000 is pulse-driven according to the present invention.

[Explanation of symbols]

 1000 Laser oscillator 100 Laser light source 200 Condenser lens 300 Laser crystal 310 First dielectric reflection film 400 Nonlinear optical medium 500 Output mirror 510 Second dielectric reflection film 600 Laser driving means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Goto 75-1, Hasunumacho, Itabashi-ku, Tokyo Inside Topcon Corporation (72) Inventor Fumio Otomo 75-1, Hasunumacho, Itabashi-ku, Tokyo Topcon Corporation Inside

Claims (8)

[Claims] 1. A laser oscillator comprising an optical resonator comprising at least a laser crystal and an output mirror, a laser light source for pumping the optical resonator, and pulse driving means for driving the laser light source. In the device, the period T of the drive pulse of the pulse drive means is
Laser oscillator with τ _FL > T-τ for τ _FL (fluorescence lifetime). (However, τ is the pulse width) 2. An optical resonator comprising at least a laser crystal and an output mirror, a non-linear optical medium inserted into the optical resonator to generate a second harmonic, and pumping to the optical resonator. A laser oscillating device comprising a laser light source for driving the laser light source and a pulse driving means for driving the laser light source, wherein the driving pulse period T of the pulse driving means is τ _FL (fluorescence lifetime) Laser oscillator with τ _FL > T-τ. (However, τ is the pulse width) 3. The pulse driving means is configured to drive the laser light source with two pulses of a first pulse and a second pulse as one set, and the first pulse is 3. The laser oscillating device according to claim 1, wherein the laser light source is driven so as not to emit light, and the second pulse is driven so that the laser light source emits light. 4. A driving method in which pulse driving is performed in order to drive a laser light source for pumping an optical resonator comprising at least a laser crystal and an output mirror, wherein a period T of the driving pulse is: A laser light source driving method in which τ _FL > T−τ with respect to τ _FL (fluorescence lifetime). (However, τ is the pulse width) 5. A pulse for driving a laser light source for pumping with respect to an optical resonator including at least a laser crystal containing a nonlinear optical medium for generating a second harmonic and an output mirror. The driving method is such that the driving pulse period T is τ _FL (fluorescence lifetime)
On the other hand, a laser light source driving method in which τ _FL > T−τ. (However, τ is the pulse width) 6. The drive pulse comprises a first pulse and a second pulse.
And the two pulses of the above pulse are set as one set to drive the laser light source, and the first pulse is
6. The laser oscillation device according to claim 4, wherein the laser light source is driven so as not to emit light, and the second pulse is driven so that the laser light source emits light. 7. A laser oscillator comprising an optical resonator comprising at least a laser crystal and an output mirror, a laser light source for pumping the optical resonator, and pulse driving means for driving the laser light source. A laser oscillation device, wherein the drive pulse of the pulse drive means has a pulse width that can obtain at least a first pulse. 8. A laser oscillator comprising an optical resonator comprising at least a laser crystal and an output mirror, a laser light source for pumping the optical resonator, and pulse driving means for driving the laser light source. In the apparatus, the drive pulse of the pulse drive means has a pulse width that can obtain at least a first pulse, and the period T of the drive pulse of the pulse drive means is τ _FL (fluorescence lifetime) with respect to τ _FL >. Laser oscillator with T-τ. (However, τ is the pulse width)