Coherent light generators – Optical fiber laser
Reexamination Certificate
1999-09-03
2001-11-20
Leung, Quyen (Department: 2881)
Coherent light generators
Optical fiber laser
C372S075000
Reexamination Certificate
active
06320885
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an upconversion fiber laser apparatus for use in displays, optical storage apparatuses, methods of processing light information, and the like.
J. Y. Allain, et al., “Blue Upconversion Fluoroziroconate Fiber Laser” Electron Lett. 26, 1990, 166 discloses the following.
When a Tm
3+
ion is pumped with two red light beams having wavelengths of 674.4 nm and 647.1 nm, respectively, it emits two light beams having wavelengths of 455 nm and 480 nm, respectively. This mechanism is called an upconversion laser. The output light of 455 nm is a pulse-like beam, whereas the output light of 480 nm is a spike-like beam. They are not continuous waves (CWs).
E. W. J. Oomen, et al., “A Material and Device Study for Obtaining A Blue Upconversion Fiber Laser” Philips J. Res. 46, 157-198, 1992 discloses an analysis of the lights the Tm
3+
ion emitted, and presents
FIGS. 2A and 2B
.
FIG. 2A
shows the energy levels a Tm
3+
ion takes, illustrating the energy transition the undergoes when pumped with light having wavelength of 650 nm. In
FIG. 2A
, the upward pointing arrows
101
,
103
, and
105
indicate absorptive transition (the ion absorbs light, thus acquiring energy). The downward pointing arrows
104
and
106
indicate radiative transition (the ion emits light, thus losing energy). The downward pointing, wavy line arrow
102
indicates non-radiative decay. The base level
3
H
6
and the other levels
3
H
4
,
3
H
5
,
3F
4
,
3
F
2.3
,
1
G
4
, and
1
D
2
shall be called “level 1,” “level 2,” “level 3,” “level 4,” “level 5,” “level 6,” “level 7” and “level 8,” respectively.
Energy exchange takes place between levels when the Tm
3+
ion is pumped with light having wavelength of 650 nm. More specifically, as the Tm
3+
ion absorbs the pump light, its energy shifts from the base level 1 to level 5 or 6 (arrow
101
). The ion stays at level 5 or 6, but for an extremely short time. It undergoes non-radiative decay; its energy decreases to level 4 (arrow
102
). The ion absorbs pump light once again, undergoing absorptive transition and, thus, shifting from level 4 to level 8 (arrow
103
). The ion then transits from level 8 to level 2 (arrow
104
). This transition is an radiative one, radiating blue light of 450 nm. The Tm
3+
ion absorbs the pump light, transiting from level 2 to level 7 (arrow
105
). The ion then undergoes radiative transition, from level 7 to the base level 1 (arrow
106
). In the course of this radiative transition, the light of 480 nm is emitted.
FIG. 2B
shows the results of the analysis of the light the Tm
3+
ion emitted when pumped with light of 650 nm. In
FIG. 2B
, the population distribution at various energy levels is plotted on the ordinate, and the optical power P (W) is plotted on the abscissa. The light emitted from the thulium (Tm) ion must be continuous waves (CWs) if it is to be used in displays. In view of the physical properties of thulium, however, it is considered extremely difficult for Tm to emit CWs at wavelength of 450 nm, though Tm can emit CWs at wavelength of 480 nm.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the first object of the present invention is to provide a means that enables an upconversion laser using Tm to emit two blue light beams having wavelengths of 450 nm and 480 nm simultaneously, both in the form of continuous waves.
The second object of the invention is to provide a similar means that realizes a blue-light upconversion laser.
To achieve the above objects, the present invention provides a hybrid fiber laser apparatus in which a super luminescence diode (SLD) chip (or laser diode chip) and an optical fiber are connected with each other at a low reflection rate, and a means for reflecting light near a wavelength A is provided at each of the other end of the laser diode chip and the other end of the optical fiber, thereby to form an optical resonator for the wavelength A. In this hybrid laser apparatus, an up-conversion fiber is provided in the optical resonator for the wavelength A, and an optical resonator structure for a wavelength B, which is constructed by a reflection means for the wavelength B, is provided at each of two positions respectively at both ends of the up-conversion fiber. Of the reflection means at the two positions, the reflection means in the laser diode chip side is arranged so as to have a high reflection rate, and the other end side is arranged to achieve partial reflection, so that output light having the wavelength B is obtained from the partial reflection side. By obtaining the resonance structure for the wavelength B described above, it is possible to extract light of a desired color.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5226049 (1993-07-01), Grubb
patent: 197 18 997 A1 (1998-11-01), None
patent: 0 450 677 A1 (1991-10-01), None
patent: 0 762 570 A2 (1997-03-01), None
J.Y. Allain, M. Monerie, H. Poignant, “Blue Upconversion Fluorozirconate Fibre Laser,” Electronics Letters, Feb. 1, 1990, vol. 26, No. 3, pp. 166-168.
E.W.J.L. Oomen and E.J. Lous, “A Material And Device Study For Obtaining A Blue Upconversion Fiber Laser,” Philips Journal of Research, 1992, vol. 46, No. 4-5, pp. 157-196. (no month available).
Itou Ken
Kawai Kiyoyuki
Okano Hideaki
Yoshida Ritsuo
Kabushiki Kaisha Toshiba
Leung Quyen
Pillsbury & Winthrop LLP
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