CN201623363U - Sweep frequency laser light source based on ultrafine tuned filter - Google Patents

Abstract

The utility model discloses a sweep frequency laser light source based on an ultrafine tuned filter. The sweep frequency laser light source is an annular laser oscillating cavity consisting of a semiconductor light amplifier, two polarization controllers, a dispersion control delay line, a circulator, an ultrafine tuned filter and an optical fibre coupler. The ultrafine tuned filter mainly comprises a double grating combined dispersion system of beam expansion grating-self-alignment grating based on a Littman-Littrow structure, and a rotary polygonal mirror. By using the dispersion capability and the beam expansion capability, the double grating layout based on the Littman-Littrow structure improves the aperture of the incident light of the self-alignment grating and also forms different deviation for the different colour lights under the self-alignment condition of the self-alignment grating to improve the angular dispersion capability of the double grating combined dispersion system; and the device can easily realize rational matching of grating parameters, incident angle and diffraction efficiency. The sweep frequency laser light source based on the ultrafine tuned filter can simultaneously ensure the ultra-fineness of the tuning and the high transmittance of the entire tuning range.

Description

A kind of frequency-sweeping laser source based on hyperfine tuned filter

Technical field

The utility model relates to the frequency sweep Optical Coherence Tomography Imaging Technology, especially relates to a kind of frequency-sweeping laser source based on hyperfine tuned filter.

Background technology

Optical coherent chromatographic imaging (Optical Coherence Tomography, be called for short OCT) can be non-invasively, with no damage the internal structure and the physiological function of biological tissue are carried out high-resolution three-dimensional imaging, in biomedical optical imagery, be used widely.Optical frequency domain imaging (frequency sweep OCT) is an OCT technology of new generation, just develops the time of more than ten years up to now, and it is to utilize tuning fast frequency-sweeping laser source in broadband and point probe to survey interference signal.But frequency sweep OCT has the feature of chromatography, high-resolution, many information, and " the optical microphotograph biopsy technology " that be expected to become on the clinical medicine implements people at highest risk's examination and clinical function such as auxiliary early diagnosis, process monitoring and operation mediation.

The resolution height be OCT than a ultrasonic big advantage that waits other imaging techniques, but the relatively low application that has limited the OCT formation method greatly of its penetration depth.The imaging depth of frequency sweep OCT is by the instantaneous live width decision of frequency-sweeping laser source.So, the frequency-sweeping laser source of acquisition long coherence length, the dark penetration depth that obtains sample is the target of various countries scholar struggle.Frequency-sweeping laser source mainly contains two kinds of frequency-selecting methods, and the one, optical fiber Fabry Perot tuned filter (fiber Fabry-Perot tunable filter, FFP-TF); The 2nd, the tuned filter of grating and polygonal rotating mirror.The FFP-TF high speed of the piezoelectric ceramic excitation of the Fujimoto group of U.S. MIT and the employings such as Chen group of University of California is tuning to be sinusoidal, two-way nonlinear scanning.The Bouma group of Harvard University, developed frequency-sweeping laser source based on the tuned filter of grating and polygonal rotating mirror, light arrives first grating and mates the face width degree of polygonal mirror and the scope of scanning angle after telescopic system changes the size of hot spot and convergent angle, realizes unidirectional, wavelength linear scanning.The Nezam of California Institute of Technology has proposed the tuned filter of grating Littrow structure and polygonal rotating mirror, and light arrives first polygonal rotating mirror and directly reflexes to the frequency-selecting of auto-collimation grating again, and this method has not had telescopic system, and structure is simple more compact.Tuned filter based on grating Littrow structure has two kinds of different forms: first kind is that collimated light returns by former road after polygonal mirror reflexes to the frequency-selecting of auto-collimation grating; Second kind is that collimated light is diffracted into to reflex on the another one face of polygonal mirror behind the auto-collimation grating after polygonal mirror reflexes to the auto-collimation grating again and returns by former road after the frequency-selecting.Second kind of form light successively shines grating three times, has improved instantaneous live width, but to the incident angle high susceptibility, is difficult to the high diffraction efficiency of coupling.People such as Canadian Leung have proposed the Li Teman structure of grating and the tuned filter of polygonal rotating mirror, and they have added a plane mirror.Expand bundle grating-reflector group assembly system for the optical grating construction of Littrow, solved the strict restriction of the height of incident angle, but instantaneous live width is still narrow inadequately, and can't avoids light beam to block phenomenon fully.The human prisms such as Changho Chong of Japan make up and carry out light and expand bundle and shine the auto-collimation grating again, improved the effectively irradiation yardstick of going up of grating, but trouble, system complex are adjusted in the prism combination.In order to improve image taking speed, Fujimoto research group, the long chamber frequency-sweeping laser source that has developed based on the Fourier mode-locking technique has substituted the short cavity frequency-sweeping laser source, and the long optical fibers that utilizes several kms is as the chromatic dispersion pilot delay line.Laser just mates with the tuning cycle of tuned filter by the required time in the long chamber of annular vibration, and each coloured light vibrates in resonant cavity simultaneously.The last restraining factors of this technology sweep velocity are sweep velocities of tuned filter, and the tuned speed that the sweep velocity of short cavity frequency-sweeping laser source then not only is subject to filter also is subject to endovenous laser settling time.

Indulging the above, how to obtain hyperfine tuned filter, obtain the frequency-sweeping laser source of narrower instantaneous live width, is big technological difficulties so that use in the demanding sample imaging of the degree of depth.

Summary of the invention

In order to overcome disadvantages of background technology, the purpose of this utility model is to provide a kind of frequency-sweeping laser source based on hyperfine tuned filter.Adopt the double grating of the expansion bundle grating-auto-collimation grating of Li Teman-Littrow structure to make up the superfine tuned filter of dispersion system and polygonal rotating mirror formation at laser oscillation cavity based on the Fourier mode-locking technique.

The technical solution adopted in the utility model is as follows:

Form annular laser oscillation cavity by semiconductor optical amplifier, first Polarization Controller, chromatic dispersion pilot delay line, circulator, tuned filter, fiber coupler and second Polarization Controller; The amplified spontaneous emission light that sends from semiconductor optical amplifier, receive the input of circulator through first Polarization Controller, chromatic dispersion pilot delay line, the Centronics port of circulator connects tuned filter, be divided into two-way behind the output termination fiber coupler of circulator, one tunnel second Polarization Controller through loop laser vibration chamber connects semiconductor optical amplifier, another road output frequency sweep laser; It is characterized in that: described tuned filter is a hyperfine tuned filter, comprises fiber optic collimator mirror, polygonal mirror, electric machine controller, expansion bundle grating, auto-collimation grating; The collimated light that comes out from the fiber optic collimator mirror reflexes to through the polygonal mirror that electric machine controller drives and to be diffracted into auto-collimation grating gating different color light after expanding the bundle grating and to reflect by former road and enter loop laser vibration chamber and form laser generation; Hyperfine tuned filter mainly is made up of double grating combination dispersion system and polygonal rotating mirror based on the expansion bundle grating-auto-collimation grating of Li Teman-Littrow structure, utilize the chromatic dispersion and expansion Shu Nengli of expanding the bundle grating, improve the bore of auto-collimation grating incident light, form different color light simultaneously the difference of auto-collimation grating auto-collimation condition is departed from, improve the angle dispersion ability of double grating combination dispersion system.

Compare with background technology, the beneficial effect that the utlity model has is:

1, based on the double grating dispersion system of Li Teman-Littrow structure, utilize the chromatic dispersion and expansion Shu Nengli of expanding the bundle grating, effectively improve the bore of auto-collimation grating incident light, form different color light simultaneously the difference of auto-collimation grating auto-collimation condition is departed from, significantly improve the angle dispersion ability of double grating combination.Conventional monochromatic light grid dispersion system, its angle dispersion can improve two orders of magnitude, has guaranteed the hyperfine tuned ability of tuned filter, realizes the tuning laser output of super narrow instantaneous live width, thereby effectively improves the imaging depth of optimal frequency domain imaging.

2, the double grating dispersion system is realized the rational Match of grating parameter, incident angle and diffraction efficiency easily, and convenient angle under high-diffraction efficiency is dynamically adjusted, and breaks through the strict angle limits in the existing monochromatic light grid layout.

3, in the double grating dispersion system, based on the expansion Shu Nengli that expands the bundle grating, improve the bore of auto-collimation grating incident light, reduced the bore requirement of incident beam on the polygonal mirror, thereby guaranteed hyperfine quick tuned filter, no light beam blocks the phenomenon generation in whole tuning range.

Description of drawings

Fig. 1 is a frequency-sweeping laser source structural representation of the present utility model.

Fig. 2 is the structural representation of hyperfine tuned filter of the present utility model.

Among the figure: 1. semiconductor optical amplifier, 2. Polarization Controller, 3. chromatic dispersion pilot delay line, 4. circulator, 5. hyperfine tuned filter, 6. fiber coupler, 7. Polarization Controller, 8. fiber optic collimator mirror, 9. polygonal mirror, 10. electric machine controller, 11. expand bundle gratings, 12. auto-collimation gratings.

Embodiment

Below in conjunction with drawings and Examples the utility model is further described:

Figure 1 shows that structural representation based on the frequency-sweeping laser source of hyperfine tuned filter.By semiconductor optical amplifier 1 (InPhenix, Inc., IPSAD1301-L213), Polarization Controller 2 (Thorlabs, Inc., PCL-35-13-SS-2-1), chromatic dispersion pilot delay line 3 (Corning, Inc., SMF28e), circulator 4 (Thorlabs, Inc., CIR-1310-50-APC), hyperfine tuned filter 5, fiber coupler 6 (Lightcomm Technology Co., Ltd., DWC-A-1*2-1315-20/80-1-0-FC/APC) and Polarization Controller 7 (Thorlabs, Inc., PCL-35-13-SS-2-1) form annular laser oscillation cavity; The amplified spontaneous emission light that sends from semiconductor optical amplifier 1, receive the input of circulator 4 through first Polarization Controller 2, chromatic dispersion pilot delay line 3, the Centronics port of circulator 4 connects the output of hyperfine tuned filter 5 frequency-selectings reflection back to circulator 4, behind fiber coupler 6, be divided into two-way, one tunnel second Polarization Controller 7 through loop laser vibration chamber connects semiconductor optical amplifier 1, another road output frequency sweep laser.

The gain media in loop laser vibration chamber is a semiconductor optical amplifier, the chromatic dispersion pilot delay line is the long optical fibers of several kms, and hyperfine tuned filter mainly is made up of double grating combination dispersion system and polygonal rotating mirror based on the expansion bundle grating-auto-collimation grating of Li Teman-Littrow structure.The amplified spontaneous emission light that sends from semiconductor optical amplifier 1, it is tuning to incide hyperfine tuned filter 5 filtering through first Polarization Controller 2, chromatic dispersion pilot delay line 3, be that the light of 3: 7 fiber couplers, 6 couplings 30% amplifies to loop laser vibration chamber gain by second Polarization Controller 7 by splitting ratio again, set up after the laser generation by be coupled 70% light of fiber coupler 6.Laser just mates with the tuning cycle of hyperfine tuned filter by the required time in loop laser vibration chamber, as shown in Equation (1).

$\frac{l_{\mathrm{cavity}}}{c}=m\·T_{\mathrm{filter}}---\left(1\right)$

In the formula, l _CavityBe the length in loop laser vibration chamber; C is the light velocity; M is an integer; T _FilterIt is the tuning cycle of hyperfine tuned filter.Fourier's mode-locking technique of the chromatic dispersion pilot delay line of this long optical fibers based on several kms, when the light of some wavelength propagates into hyperfine tuned filter 5 through long chamber, filter just be tuned to the light of this wavelength is passed through window, each coloured light is vibrated in loop laser vibration chamber simultaneously, thereby obtained quasi-continuous pattern output.Therefore, sweep velocity no longer is subjected to each coloured light to set up the time restriction of vibration at the laser in chamber, and only is subject to the sweep speed of combined tuned filter.The mode competition of long endovenous laser vibration has also improved the instantaneous live width of frequency sweep laser simultaneously.

Figure 2 shows that the structural representation of hyperfine tuned filter.Hyperfine tuned filter 5 comprises fiber optic collimator mirror 8 (OZ Optics, Inc., HPUCO-23A-1300/1500-S-10AC), polygonal mirror 9 (LincolnLaser Co., Ltd., SA34/DT-72-250), electric machine controller 10 (Lincoln Laser Co., Ltd., MC-5), grating 11 (Newport, Inc., 53-*-540R) and auto-collimation grating 12 (Newport, Inc., 53-*-540R); The polygonal mirror 9 that the collimated light that fiber optic collimator mirror 8 comes out drives through electric machine controller 10 reflexes to and expands the back frequency-selecting that is diffracted into auto-collimation grating 12 of bundle grating 11 and return by former road and enter loop laser resonance cavity formation laser generation.Polygonal mirror 9 rotations that electric machine controller 10 drives realize from λ ₁To λ _nTuning, corresponding angular range Δ θ.

Hyperfine tuned filter mainly is to be made of double grating combination dispersion system and polygonal rotating mirror based on the expansion bundle grating-auto-collimation grating of Li Teman-Littrow structure.The double grating combined system can obtain great angle dispersion, thereby realizes super narrow instantaneous live width.

The grating of Littrow structure is operated in the auto-collimation state, and at this moment the angle of diffraction equals incidence angle

Grating equation is

In the formula, d is a grating constant; For incidence angle also is the angle of diffraction; M is the optical grating diffraction level; λ is an optical wavelength.When grating constant d and order of diffraction m determine, will be the angle by the tuning laser wavelength X

Function.When polygonal rotating mirror, the angle of light and the angle of diffraction continuously change, and at this moment satisfy the wavelength of Littrow condition, promptly realize tuning.Formula (2) is to the wavelength X differentiate, and the angle dispersion formula that obtains grating is

Under expansion bundle grating-arrangement of mirrors system situation that the grating of Li Teman structure becomes with the plane reflector group, light with the wide-angle glancing incidence to grating.Big angle incident, the grating of little angle outgoing work are to expand the bundle grating.At this moment have only after the speculum feedback,, just can enter laser oscillation cavity and form laser generation along the corresponding wavelength that original optical path returns.The return light of feedback, to becoming the bundle grating then with small-angle incidence, big angle outgoing, the grating bundle grating that become to contract at this moment.Light round trip, twice irradiation become one way angle dispersion that the bundle grating produces into

$\frac{\mathrm{d\α}}{\mathrm{d\λ}}=\frac{2m}{d\cos \mathrm{\α}}---\left(4\right)$

In the formula, α is the incidence angle of grating.This will double under the auto-collimation state than same grating.

The expansion bundle grating that the double grating of Li Teman-Littrow structure is formed-auto-collimation grating combination dispersion system has only after auto-collimation grating feedback, along the corresponding wavelength that original optical path returns, just can enter laserresonator and form laser generation.Light round trip, twice irradiation become bundle grating, once irradiating auto-collimation grating.Expanding bundle grating-total angle dispersion of auto-collimation grating double grating combination dispersion system is

In the formula, M is the expansion bundle rate that expands the bundle grating, is the ratio of optical grating diffraction light beam beamwidth and incident beam beamwidth.Compare this formula and formula (3) and (4), and first on equal sign the right is and becomes the chromatic dispersion of bundle grating self, and second is that light expansion bundle rate M is multiply by in the auto-collimation grating dispersion.Formula shows that becoming the bundle grating not only has light to become Shu Zuoyong, and tuning grating dispersion has amplification to auto-collimation, has improved angle dispersion greatly.The double grating dispersion system is not how much additions of the angle dispersion of two gratings, and expanding bundle grating pair auto-collimation grating has amplification, thereby can obtain hyperfine chromatic dispersion.The double grating dispersion system is realized the rational Match of grating parameter, incident angle and diffraction efficiency easily than the monochromatic light grating system of existing Littrow structure, and convenient angle under high-diffraction efficiency is dynamically adjusted.In the double grating dispersion system,, improve the bore of auto-collimation grating incident light, reduced the bore requirement of incident beam on the polygonal mirror, thereby guaranteed hyperfine tuned time, at whole tuning range λ based on the expansion Shu Nengli that expands the bundle grating ₁To λ _nIn (corresponding angular range Δ θ) no light beam block phenomenon and take place, and the face width degree of polygonal mirror can have and hang down requirement, thus the face that can improve the small reflector of polygonal mirror is counted N, improves sweep velocity thus.

Present embodiment is based on the 1300nm wave band, but the utility model also can be applicable to its all bands such as 1060nm wave band.

The frequency-sweeping laser source of the disclosed a kind of hyperfine tuned filter of the utility model adopts in the loop laser of Fourier mode-locking technique vibration chamber that to carry out filtering based on the double grating combination dispersion system of the expansion bundle grating-auto-collimation grating of Li Teman-Littrow structure and hyperfine tuned filter that polygonal rotating mirror constitutes tuning.Hyperfine tuned filter significantly improves the angle dispersion ability of double grating combination; And convenient angle under high-diffraction efficiency is dynamically adjusted; Guaranteed that no light beam blocks features such as phenomenon generation in the hyperfine quick tuning range.Frequency-sweeping laser source based on hyperfine tuned filter is significant at the demanding optimal frequency domain imaging technique of imaging depth.

Claims (1)

1. the frequency-sweeping laser source based on hyperfine tuned filter is formed annular laser oscillation cavity by semiconductor optical amplifier (1), first Polarization Controller (2), chromatic dispersion pilot delay line (3), circulator (4), tuned filter, fiber coupler (6) and second Polarization Controller (7); The amplified spontaneous emission light that sends from semiconductor optical amplifier (1), receive the input of circulator (4) through first Polarization Controller (2), chromatic dispersion pilot delay line (3), the Centronics port of circulator (4) connects tuned filter, be divided into two-way behind the output termination fiber coupler (6) of circulator (4), one tunnel second Polarization Controller (7) through loop laser vibration chamber connects semiconductor optical amplifier (1), another road output frequency sweep laser; It is characterized in that: described tuned filter is hyperfine tuned filter (5), comprises fiber optic collimator mirror (8), polygonal mirror (9), electric machine controller (10), expands bundle grating (11), auto-collimation grating (12); The collimated light that comes out from fiber optic collimator mirror (8) reflexes to through the polygonal mirror (9) that electric machine controller (10) drives and to be diffracted into auto-collimation grating (12) gating different color light after expanding bundle grating (11) and to reflect by former road and enter loop laser vibration chamber and form laser generation; Hyperfine tuned filter mainly is made up of double grating combination dispersion system and polygonal rotating mirror based on the expansion bundle grating-auto-collimation grating of Li Teman-Littrow structure, utilize the chromatic dispersion and expansion Shu Nengli of expanding bundle grating (11), improve the bore of auto-collimation grating (12) incident light, form different color light simultaneously the difference of auto-collimation grating (12) auto-collimation condition is departed from, improve the angle dispersion ability of double grating combination dispersion system.

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