CN102751653A - Photonic crystal fiber based medium-infrared optical fiber parametric oscillator for degenerating four-wave mixing - Google Patents

Abstract

A mid-infrared fiber parametric oscillator based on photonic crystal fiber degenerate four-wave mixing relates to a laser oscillator. A laser pump source, focusing lens system, 4 reflectors, and photonic crystal fiber are provided; the laser pump source, focus lens system, 4 reflectors, and photonic crystal fiber are sequentially connected in series to form an optical fiber ring cavity, and the laser pump The source is coupled into the photonic crystal fiber through the focusing lens system, and four mirrors ensure that the signal light in the visible light band oscillates and lases in the ring cavity, and the coherent mid-infrared idler light is output from the end of the photonic crystal fiber. The pump laser in the 1030-1070nm band is coupled to the photonic crystal fiber to excite the nonlinear effect of four-wave mixing in the fiber, and the laser output in the mid-infrared band is realized. The resonant cavity structure of the oscillator is composed of four mirrors to ensure that the signal light in the visible band is completely reflected in the cavity, and the coherent idler light in the mid-infrared band is completely output from the end of the photonic crystal fiber, and the conversion efficiency is high.

Description

Mid-infrared fiber parametric oscillator based on photonic crystal fiber degenerate four-wave mixing

technical field

The invention relates to a laser oscillator, in particular to a mid-infrared optical fiber parametric oscillator based on photonic crystal optical fiber degenerate four-wave frequency mixing.

Background technique

Mid-infrared laser sources have important application value and prospects in both military and civilian applications. There are many technical approaches to realize mid-infrared lasers, which can be mainly divided into four categories, namely: (I) semiconductor quantum cascade lasers ([1] P.Q.Liu, A.J.Hoffman, M.D.Escarra, K.J.Franz, J.B.Khurgin, Y. Dikmelik, X.Wang, J.-Y.Fan, and C.F.Gmachl, "Highly power-efficient quantum cascade lasers", Nat.Photon.,vol.4(2),pp.95-98,2010); (II ) Rare earth crystal laser ([2] K.S.Lai, W.J.Xie, R.F.Wu, Y.L.Lim, E.Lau, L.Chia, and P.B.Phua, "A 150W 2-micron diode-pumped Tm:YAG laser," in Proceedings on Advanced Solid-StateLasers (OSA), vol.68, pp.535-539, 2002, Washington); (III) Solid-state crystal optical parametric oscillator (OPO) ([3]T.J.Carrig and A.M.Schober,"Mid-Infrared lasers", Photonics Journal, vol.2(2), pp.207-212, 2010); (IV) Rare-earth-doped fiber lasers ([4] P.F.Moulton, G.A.Rines, E.V.Slobodtchikov, K.F.Wall, G.Frith, B . Samson, and A.L.G. Carter, "Tm-doped fiber lasers: fundamentals and powerscaling", IEEE J. Sel. Topics in Quantum Electron., 15(1), pp.85-92, 2009). In addition, mid-infrared lasing can also be generated by free-electron lasers, chemical lasers, and gas laser frequency doubling/difference frequencies, but its high price and complex structure make it difficult to attract attention. The above (I)-(IV) technologies all have their advantages, but also have their own disadvantages. Although semiconductor quantum cascade technology has obvious advantages in obtaining miniaturized and broadband mid-infrared lasers, it has a large divergence angle, poor beam quality, and most of them operate at extremely low temperatures due to thermal management problems, resulting in limited output power. Rare earth-doped crystal laser technology still has some shortcomings, mainly reflected in: (1) The crystal has poor heat dissipation, and the strong thermal effect usually requires some special cooling methods and equipment; (2) The use of a large number of block optical components makes the laser system complex. On the other hand, when the crystal OPO technology is used, the walk-off effect is strong, the phase matching conditions must be precisely designed, and many bulk optical devices need to be cumbersomely collimated. In comparison, mid-infrared rare earth-doped fiber lasers can make up for the above (I)-(III) mid-infrared lasers to a certain extent due to their significant advantages such as high conversion efficiency, good heat dissipation, high beam quality, high power, and easy integration. Insufficient laser source. However, the mid-infrared lasing >3 μm band of rare-earth-doped optical fiber is still a technical bottleneck in this field, and there are few reports so far. Based on the above analysis, an ideal solution is to use OPO technology in optical fibers. The emergence of photonic crystal optical fibers (such as fluoride glass and telluride glass, pure silica, etc.) has undoubtedly brought great opportunities for it. By designing the photonic crystal fiber waveguide parameters, the zero-dispersion wavelength and nonlinear coefficient of the photonic crystal fiber can be flexibly controlled, and these parameters will help greatly improve the efficiency of parametric oscillation. Because of this, it has attracted popular research and successfully obtained the mid-infrared laser based on photonic crystal fiber ([5]Amir Herzog, Avishay Shamir, and Amiel A.Ishaaya.OpticsLetters.Wavelength conversion of nanosecond pulses to the mid-IR in photonic crystal fibers.2012,37(1):82-84; [6]D.Nodop,C.Jauregui,D.Schimpf,J.Limpert,and A.Tunnermann.OpticsLetters.Efficient high-power generation of visible and mid-infrared light by degeneratefour-wave-mixing in a large-mode-area photonic-crystal fiber.2009,34(22):3499-3501), however, the common point of these current studies is that they do not constitute a laser cavity, Furthermore, the coherence of the output beam is not good, and the conversion efficiency is low.

Contents of the invention

The object of the present invention is to provide a mid-infrared fiber parametric oscillator based on photonic crystal fiber degenerate four-wave mixing.

The present invention is provided with laser pumping source, focusing lens system, 4 reflection mirrors, photonic crystal fiber; Said laser pumping source, focusing lens system, 4 reflection mirrors, photonic crystal fiber are sequentially connected in series to form the optical fiber annular cavity, laser The pump source is coupled into the photonic crystal fiber through the focusing lens system, and the four mirrors ensure that the signal light in the visible light band oscillates and lases in the ring cavity, and the coherent mid-infrared idler light is output from the end of the photonic crystal fiber.

The laser pumping source can be a 1030-1070nm band ytterbium-doped fiber laser or the like.

The material of the photonic crystal fiber can be selected from fluoride glass, telluride glass or pure silicon dioxide.

The invention adopts 1030-1070nm band pumping laser to couple to the photonic crystal fiber, excites the fiber four-wave mixing nonlinear effect, and realizes the mid-infrared band laser output. The resonant cavity structure of the oscillator is composed of four mirrors to ensure that the signal light in the visible band is completely reflected in the cavity, and the coherent idler light in the mid-infrared band is completely output from the end of the photonic crystal fiber, and the conversion efficiency is high.

The invention is a mid-infrared parametric oscillator based on photonic crystal fiber, which adopts a structure of full feedback of signal light and full output of mid-infrared idler light. The results show that the invention can significantly improve the coherence and conversion efficiency of the mid-infrared laser.

Description of drawings

FIG. 1 is a schematic diagram of the structure and composition of an embodiment of the present invention. In Figure 1, mark A is the input of the laser pump source, and B is the output of the laser in the mid-infrared band.

Fig. 2 is a typical phase matching curve of an embodiment of the present invention (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). In Fig. 2, the horizontal axis is the wavelength of pump light (λ _pump [μm]), and the vertical axis is the wavelength of signal and idler light (λ _signal , λ _idler [μm]).

Fig. 3 is the threshold curve of the embodiment of the present invention (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). In Figure 3, the horizontal axis represents the length of the photonic crystal fiber (Length of PCF[m]), and the vertical axis represents the threshold pump power (Threshold power[W]).

Fig. 4 shows the oscillation characteristics of intracavity pump light, signal light and idler light according to the embodiment of the present invention (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). In Figure 4, the horizontal axis represents the position of the photonic crystal fiber (Z[m]), and the vertical axis represents the power of pump light, signal light and idler light (Pump power, Signal power, Idler power[W]).

Fig. 5 shows the variation of the efficiency of the embodiment of the present invention with the length of the fiber and the pump power (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). In Figure 5, the horizontal axis represents the length of the photonic crystal fiber (Length of PCF[m]), and the vertical axis represents the conversion efficiency of mid-IR idler light (Conversion efficiency of mid-IR idler[%]).

Detailed ways

Referring to Fig. 1, the embodiment of the present invention is provided with a laser pump source, a focusing lens system 2, and 4 mirrors (the first mirror 3, the second mirror 4, the third mirror 5, and the fourth mirror 6), Photonic crystal fiber 7; the laser pumping source, focusing lens system 2, 4 mirrors (first mirror 3, second mirror 4, third mirror 5, fourth mirror 6), photonic crystal fiber 7 are sequentially connected in series to form a fiber ring cavity, the laser pumping source is coupled into the photonic crystal fiber 7 through the focusing lens system 2, and the four mirrors 3-6 ensure that the signal light in the visible band oscillates and lases in the ring cavity, and the photonic crystal fiber 7 The end outputs coherent mid-infrared idler light.

The laser pumping source adopts 1030-1070nm band ytterbium-doped fiber laser or the like.

The material of the photonic crystal fiber 7 is selected from fluoride glass, telluride glass or pure silicon dioxide.

Taking the 1030nm pump source and NKT photonic crystal fiber (silica material) as the gain medium as an example to illustrate the specific implementation.

Mark A is the 1030nm ytterbium-doped fiber laser pump output.

The focusing lens system 2 couples the pump laser light into the photonic crystal fiber 7 .

The reflection wavelength of the first reflector 3 is about 640nm, and the reflectivity is greater than 99%.

The reflection wavelength of the second reflection mirror 4 is about 640nm, and the reflectivity is greater than 99%.

The reflection wavelength of the third reflecting mirror 5 is about 640nm, and the reflectivity is greater than 99%.

The reflection wavelength of the fourth reflecting mirror 6 is about 640nm, and the reflectivity is greater than 99%.

Photonic crystal fiber 7 (NKT-LMA-8) has a length of 1 m, a core diameter of 8 μm, an air hole diameter of 2.42 μm, and an air hole-to-air hole spacing of 5.5 μm, which is used as a nonlinear material for four-wave mixing.

Mark 8 is the signal light in the visible light band reflected in the cavity, forming a laser to oscillate in the cavity.

Mark B is the laser output in the mid-infrared band.

Figure 2 shows a typical phase matching curve of the embodiment of the present invention (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). It can be seen from Figure 2 that corresponding to a pump wavelength, there is always a signal light and an idler light matching it, for example, for a 1030nm pump, the signal and idler light wavelengths of its parametric gain are 0.641μm and 2.611μm respectively .

Figure 3 shows the threshold curve of the embodiment of the present invention (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). It can be seen from Fig. 3 that within a certain range, as the fiber length increases, the threshold pump power decreases gradually.

Figure 4 shows the oscillation characteristics of the intracavity pump light, signal light and idler light in the embodiment of the present invention (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). It can be seen from Figure 4 that when the pump light is at the peak, it corresponds to the trough of the signal and idler frequency; when the pump light is at the trough, it corresponds to the peak of the signal and idler frequency, which proves the energy exchange process between the intracavity pump, signal and idler frequency .

Fig. 5 shows the variation of the efficiency of the embodiment of the present invention with the length of the fiber and the pump power (taking pure silicon NKT LMA-8 photonic crystal fiber as an example). It can be seen from Figure 5 that, with the fixed pump power, as the length of the fiber increases, the efficiency fluctuates as shown in the figure. The reason for this change is mainly the influence of the length of the fiber on the phase matching. The peak position of the volatility change gradually decreases, that is, the efficiency decreases; at the same time, the tolerance length bandwidth is defined in the figure, and as the pump power increases, the tolerance length bandwidth gradually decreases, that is, to achieve a better The parametric gain is more sensitive to the choice of fiber length as the pump power increases.

Claims (3)

1. based on the middle infrared optical fiber parametric oscillator of photonic crystal fiber degeneration four-wave mixing, it is characterized in that being provided with laser pumping source, focus lens system, 4 speculums, photonic crystal fiber; Said laser pumping source, focus lens system, 4 speculums, photonic crystal fibers are concatenated into fiber optic loop an actor's rendering of an operatic tune successively; Laser pumping source is coupled into photonic crystal fiber through focus lens system; The flashlight of 4 speculum assurance visible light wave ranges vibrates to swash in annular chamber and penetrates, infrared ideler frequency light during the terminal output of photonic crystal fiber is relevant.

2. the middle infrared optical fiber parametric oscillator based on the photonic crystal fiber degeneration four-wave mixing as claimed in claim 1 is characterized in that said laser pumping source adopts 1030～1070nm wave band ytterbium-doping optical fiber laser etc.

3. the middle infrared optical fiber parametric oscillator based on the photonic crystal fiber degeneration four-wave mixing as claimed in claim 1 is characterized in that the material of said photonic crystal fiber is selected from fluoride glass, tellurite glass or pure silicon dioxide.

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