JP2003270686A - Structure for ld fiber pigtail second harmonic output laser resonator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LD fiber pigtail internal resonator second harmonic laser for efficiently converting light from a near infrared wavelength laser diode to light having a visible wavelength. <P>SOLUTION: As shown in Figures 1, 2, and 3, a nonlinear optical crystal is arranged in an LD resonator composed of a Back Facet coated with a total reflection film and a fiber pigtail-side total reflection fiber Bragg diffraction, thereby constituting the LD fiber pigtail second harmonic output resonator which efficiently converts a near infrared LD wavelength to a visible wavelength. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a fiber pigtail diode laser (LD, Laser Diode).
e) Second harmonic visible wavelength output laser resonator structure.

[0002]

2. Description of the Related Art Conventionally, a near-infrared wavelength fundamental wave laser of a free space output laser diode (LD, Laser Diode) is used to generate a second harmonic SHG (Second Harmonic Gene) using a nonlinear optical crystal.
There is a technique for converting the wavelength into a visible wavelength.

[0003]

Laser diode L
The output wavelength of D is generally from near infrared to red 630 nm
However, many applications, such as laser-based measurement and analysis equipment, require visible wavelengths shorter than the laser diode output.

The wavelength conversion output from the LD to the visible is normally converted from a solid laser of a crystal such as YAG having a near-infrared wavelength of LD excitation to a second harmonic, but the optical configuration becomes complicated. Although a method of directly converting the wavelength of the near-infrared wavelength of the LD into the second harmonic has been recently developed, the wavelength conversion from the LD to the second harmonic with high efficiency is an unsolved problem. The problem to be solved by the present invention is to efficiently convert the wavelength of the second harmonic from the LD of the near infrared wavelength to the visible wavelength by using the nonlinear optical crystal.

[0005]

[Means for Solving the Problems] Back fasc
Facet), total reflection thin film, front fasit (Fr
(ont facet) LD with an antireflection film is condensed by a lens or the like to obtain a fiber Bragg grating FB having a high reflectance.
The mechanism to input and oscillate in the optical fiber with G is
It is called a fiber pigtail LD. In recent years, near-infrared wavelength fiber pigtail output LDs are often used in optical communication, and such products are very excellent in terms of output stability and long-term operation reliability.

By using such a fiber pigtail technology of a communication-related LD, that is, a technology of inputting the LD into a fiber pigtail having an FBG that reflects the oscillation wavelength and causing the LD to oscillate, a wavelength conversion nonlinear optical crystal element is provided in the same oscillator. The provision of the laser to output the second harmonic through the fiber pigtail is a means for solving the problem of efficiently converting the near infrared wavelength of the LD into the visible wavelength of the second harmonic.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Since the second harmonic visible wavelength laser output is obtained directly from a single transverse mode LD, the present invention provides a laser resonator for a fiber pigtail LD second harmonic output as shown in FIGS. Devised.

Since the invention is also applied to the case where the pumping light source is a multi-transverse mode LD, a structure of a laser resonator for outputting a fiber pigtail LD second harmonic as shown in FIG. 3 was also devised.

First, the mechanism of the laser oscillator will be described. Backfacto of the fundamental wave light source LD10 (Back
Facet 11 is coated with a total reflection film for the oscillation wavelength of the LD, and the front facet of the LD output side (Front F
The light from the LD, which is collected by a lens or the like and input into the fiber, is totally reflected by the fiber Bragg grating FBG 60, and the FBG 60
Serves as the other reflecting mirror for lasing. Such a structure becomes an LD fundamental wave oscillator.

The non-linear optical element 50 for converting the wavelength to the second harmonic is placed in the resonator of the LD fundamental wave, and the second harmonic wave S is produced by the intra-cavity method.
HG (Second Harmonic Genera
wavelength). Since the optical path passes through the fiber pigtail, a pair of collimator systems 40 as shown in FIGS. 1 and 2 or a one-sided collimator 40 as shown in FIG. 3 is provided.
An HG nonlinear optical element is installed.

Regarding the optical path connection between the LD and the fiber, that is, the method of inputting the LD into the fiber, in the case of a single mode linearly polarized LD light source, an aspherical lens 20 as shown in FIG. 1 or as shown in FIG. The polarization maintaining fiber 30 is formed by condensing the laser beam of the LD at the wedge type fiber end face 70.
To enter. In the case of a multimode LD, as shown in FIG. 3, the light is input to the fiber pigtail through the collimator lens systems 20 and 21, or a polarizing element 80 such as a silica glass plate placed at the Brewster angle with the laser optical axis.

As described above, the LD of the fundamental wave is oscillated by the fiber pigtail resonator which constitutes the two total reflection surfaces of the back fascite 11 and the FBG 60, and the nonlinear optical crystal 50 is further oscillated by the intracavity method. Then, the wavelength is converted into the second harmonic, and the fiber pigtail is caused to output the visible light of the second harmonic from the LD of the near infrared wavelength.

[0013]

[Embodiment] Near infrared wavelength 800 with the structure shown in FIGS.
Using a LD from 1 nm to 1550 nm, the laser output of the fiber pigtail second harmonic is in the wide wavelength range from visible 400 nm to near infrared 775 nm. Specifically, referring to FIG. 1, an embodiment of a fiber pigtail output laser for the LD of 1120 nm near infrared wavelength to the yellow visible wavelength of the second harmonic 560 nm will be described below.

The back facet 11 of the LD laser 10 having a wavelength of 1120 nm is coated with a total reflection film having a wavelength of 1120 nm. 112 on the front facade 12 of the LD10
An antireflection film is coated on the 0 nm wavelength, the laser beam is condensed by the lens 20 and is input to the polarization maintaining PM fiber 30, and is reflected by the fiber Bragg grating 60 that totally reflects the 1120 nm wavelength. It is composed of a fiber pigtail laser resonator. On the other hand, a nonlinear optical crystal KTP (KTiOPO ₄ , Potassium Tit) for converting the second harmonic visible light into a wavelength of 560 nm.
11 for placing any Phosphate) inside the 1120 nm fundamental wave fiber pigtail type resonator.
A pair of 20 nm wavelength collimator system 40 is provided. In this way, since the wavelength conversion element is installed inside the resonator, the light intensity of the fundamental wave laser LD is tens of times stronger than the outside of the cavity, so that the conversion efficiency is proportional to the square of the fundamental wave intensity. The non-linear effect of becomes stronger. The wavelength conversion element 5
Regarding 0, quasi-phase-matched periodic polarization PPKTP
The nonlinear optical effect can be enhanced by using (Periodically Poled KTP).

[0014]

EFFECTS OF THE INVENTION With the relatively simple LD fiber pigtail second harmonic resonator structure as described above, a continuous wave output laser of 560 nm yellow wavelength of several mini watts class is used by using a 1120 nm wavelength LD of 100 mW class power. Is obtained. Thus, a fiber pigtail second harmonic laser using an LD in the wavelength range of 800 nm to 1400 nm can realize a laser having an output in a wide visible wavelength range from 400 nm to 700 nm.

[Brief description of drawings]

FIG. 1 is a block diagram of a second harmonic output LD fiber pigtail laser in which a single mode LD light is input to a fiber by a lens.

FIG. 2 is a configuration diagram of a second harmonic output LD fiber pigtail laser in a method of inputting light of a single mode LD from an end face of a fiber with a wedge.

FIG. 3 is a configuration diagram of a second harmonic output LD fiber pigtail laser in a system in which light of a multimode LD is input to a fiber in a lens collimator system.

[Explanation of symbols]

(10) Laser diode (LD), pumping light source for second harmonic laser. (11) Back face of LD (Back Face)
t), a total reflection film is coated on the LD oscillation wavelength. (12) Front Fasit of LD (Front Fa
cet), and an LD oscillation wavelength is coated with an antireflection film. (20) A condenser lens for inputting LD light into the fiber. (21) A collimator lens for inputting the LD light into the fiber. (30) Polarization maintaining fiber. (40) Fiber collimator. (50) A phase-matching nonlinear optical crystal or a periodic polarization (Periodical Poled) nonlinear optical crystal, which is an element for wavelength-converting an LD fundamental wave into a second harmonic. (60) The fiber Bragg grating element has a high reflectance at the center wavelength of the LD oscillation and serves as a total reflection mirror of the laser resonator. (70) Wedge type fiber end face. (80) A polarizing element, a quartz plate placed at Brewster's angle, a via fringe crystal, or the like.

Claims (2)

Number of claims 2 [Claims] 1. A second harmonic output in a structure in which a non-linear optical crystal is provided inside a fiber pigtail type single mode laser diode resonator having a fiber Bragg grating (FBG) as shown in FIGS. 1 and 2. LD fiber pigtail laser. 2. A second harmonic output LD fiber pigtail laser having a structure in which a nonlinear optical crystal is provided inside a fiber pigtail type multimode LD resonator having an FBG as shown in FIG.