CN104181746B - Optical time domain Fourier transformer - Google Patents
Optical time domain Fourier transformer Download PDFInfo
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- CN104181746B CN104181746B CN201410391247.0A CN201410391247A CN104181746B CN 104181746 B CN104181746 B CN 104181746B CN 201410391247 A CN201410391247 A CN 201410391247A CN 104181746 B CN104181746 B CN 104181746B
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Abstract
The invention provides an optical time domain Fourier transformer, and belongs to integrated photonic devices. Compared with the conventional optical time domain Fourier transformer, the optical time domain Fourier transformer provided by the invention can realize integration and smaller design size, and comprises a cladding layer, a lower guided wave layer and an upper guided wave layer which are sequentially grown on a substrate from the bottom up; the upper guided wave layer is a graphics layer, and comprises an input waveguide, a first collimation lens, a first blazed raster, a second collimation lens, a Fourier transform lens, a third collimation lens, a second blazed raster, a fourth collimation lens and an output waveguide which are sequentially arranged in the z direction, and are made of the same material. The optical time domain Fourier transformer is small in size and compatible with a conventional production process, can realize monolithic integration conveniently, and can realize a Fourier transform function on pulses of the input time in an ultrashort optical pulse communication system.
Description
Technical field
The invention belongs to integrated photonic device, and in particular to a kind of optical time domain Fourier transformer.
Background technology
In the last few years, Ultrashort pulse technology achieved revolutionary progress, and time lens rise in Ultrashort pulse technology
To important function, it is mainly used in pulse compression technique, time image technology, and the field such as orthogonal frequency division multiplexi.
Traditional optical time domain Fourier transformer by be input into dispersive medium, introduce second order phase modulation time lens,
Output dispersive medium composition.Because the time lens based on electric light phase-modulation are easily achieved, stable performance, therefore with electric light phase
Position manipulator is most common method as time lens.But because electro-optic phase modulator can only enter in modulation immediate vicinity
The approximate second order phase modulation of row, causes time lens to be limited by aperture, in addition the time lens based on electric light phase-modulation
One major issue of the time image system of composition is that resolution is relatively low.See Quantum Electronics, IEEE
Journal of,2000.36(4):P.430-437. additionally, time lens can also be using nonlinear crystal and frequency and difference frequency
And the Cross-phase Modulation of light is realizing.Above-mentioned several implementation methods are all to use discrete photoelectric device, therefore just
Have and be difficult to integrated difficult and relatively large physical dimension.Recently, Cornell University of the U.S. has put forward one kind in silicon
The time lens based on four-wave mixing (FWM) effect completed on based optical waveguide, they are with two such four-wave mixing lens
Constitute a Time telescope system.This time lens can have more than the phase shift of 100 π to input pulse, but utilize
Four-wave mixing effect will increase the amplitude noise that input pulse is produced, and high for operation wavelength precise requirements, and
Need to produce specific pumping light pulse.See " Silicon photonics:Silicon's time lens,"Nat
Photon,vol.3,pp.8-10,2009.
The content of the invention
The technical problem to be solved is：Offer one kind has small volume compatible with existing processing technology and can
Single chip integrated optical time domain Fourier transformer is easily carried out, it is in ultrashort light pulse communication system, it is possible to achieve right
The time domain Fourier transformation function of input time pulse, belongs to integrated photonic device.
The present invention solves its technical problem and adopts following technical scheme：
The present invention provide optical time domain Fourier transformer, its by the covering grown successively from bottom to top on substrate,
Lower ducting layer and upper ducting layer are constituted.
The optical time domain Fourier transformer is based on Planar Lightwave Circuit Technology, by any Jie that can form planar optical waveguide
Material is realized, compatible with existing processing technology, can be made by the standard lithographic of Planar waveguide technology and etching technics, volume
Little, being capable of the device of easily material system identical with other carries out single-chip integration.
The upper ducting layer is graph layer, is dodged by the input waveguide being arranged in order in the z-direction, the first collimating lens, first
It is credit grating, the second collimating lens, Fourier transform lens, the 3rd collimating lens, the second balzed grating, the 4th collimating lens, defeated
Go out waveguide composition.
The substrate is made up of the dielectric material that can form planar optical waveguide, and the material includes monocrystal silicon, indium phosphide, arsenic
Change gallium, sapphire or carborundum.
The covering is made up of the dielectric material that can form planar optical waveguide, the material include silicon dioxide, indium phosphide,
InGaAsP, GaAs, aluminum gallium arsenide, gallium nitride, indium gallium nitrogen or aluminum gallium nitride.
The upper ducting layer and the employing of lower ducting layer can form the dielectric material of planar optical waveguide, and the material includes non-
Crystal silicon, InGaAsP, GaAs, gallium nitride, indium gallium nitrogen or aluminum gallium nitride.
The above-mentioned optical time domain Fourier transformer that the present invention is provided, its purposes is：The optical time domain Fourier transformer
When applying in ultrashort light pulse communication system, the accurate time domain Fourier transformation work(to input time pulse can be realized
Energy.
When the optical time domain Fourier transformer is applied in ultrashort light pulse communication system, comprise the following steps：
A. light pulse is incident from input waveguide, receives in output waveguide；
B. the first collimating lens, the 3rd collimating lens play the role of to collimate light, and in its focal plane directional light is obtained；
C. the second collimating lens, the 4th collimating lens play the role of to focus on light, and in its focal plane focal beam spot is obtained；
D. first balzed grating, plays a part of light splitting, and the light of different frequency has different deflection sides after grating
To finally the light of different frequency component being focused on the diverse location of the focal plane of the second collimating lens；Second balzed grating,
Effect and the effect contrast of the first balzed grating, the light of all frequency components of different directions propagation is changed into along same
The directional light that direction is propagated；
E. the effect of the Fourier transform lens is to carry out spatial fourier transform, and behind focal plane obtains input field
Spatial fourier transform.
The present invention has compared with prior art following major advantage：
1. the present invention can be made by the standard lithographic of Planar waveguide technology and etching technics, collimating lens in upper ducting layer,
The top surface of balzed grating, and Fourier transform lens is same level for the top surface of same level, input waveguide and output waveguide
Face.The present invention is based on Planar Lightwave Circuit Technology, can be realized by any dielectric material that can form planar optical waveguide, with existing system
Make process compatible, small volume, and can the device of easily material system identical with other carry out single-chip integration, therefore have relatively
Low manufacturing cost.
2. the invention belongs to optical passive component, it is not necessary to device itself plus any type of signal of telecommunication, optical signal conduct
Driving source.
3. the integral device size of the present invention is 600 μm (width) * 350 μm of (height) * 5mm (length), and traditional light
Class hour, domain Fourier transformer was mainly made up of the discrete optics such as electro-optic phase modulator and single mode dispersive optical fiber, wherein electricity
Optical phase modulator typically has a size of tens or hundreds of millimeters, the Lithium metaniobate electro-optic phase modulator of such as U.S. EOSPACE productions,
Its size is 88.4*8.9*8.9mm, and the length of single mode dispersive optical fiber is generally hundreds of rice.Therefore the present invention is compared with traditional light
Class hour, domain Fourier transformer had the size of very little.
Description of the drawings
Fig. 1 is the structural representation in the y directions of the present invention.
Fig. 2 is the top view of the present invention.
Fig. 3 is collimating lens top view.
Fig. 4 is balzed grating, top view.
Fig. 5 is Fourier transform lens top view.
Fig. 6 is time domain output waveform diagram.
Fig. 7 is the input pulse schematic diagram of two different pulse widths.
Fig. 8 is the output pulse schematic diagram of the input pulse of two different pulse widths that emulation is obtained.
In figure：1. input waveguide；2. the first collimating lens；3. the first balzed grating,；4. the second collimating lens；5. Fourier
Transform lenses；6. the 3rd collimating lens；7. the second balzed grating,；8. the 4th collimating lens；9. output waveguide；10. ducting layer is gone up；
11. times ducting layer；12. coverings；13. substrates.
Specific embodiment
With reference to embodiment and accompanying drawing, the invention will be further described, but does not limit the present invention.
The optical time domain Fourier transformer that the present invention is provided, its structure as shown in figure 1, by substrate 13 from lower
On the covering 12, lower ducting layer 11 and the upper ducting layer 10 that grow successively constitute, wherein：Substrate 13 is crystalline silicon, and covering 12 is two
Silicon oxide, lower ducting layer 11 and upper ducting layer 10 are non-crystalline silicon.
The covering 12 is 0.5 micron from the height in x directions.
The lower ducting layer is 0.45 micron from the height in x directions.
Referring to Fig. 2, the upper ducting layer is graph layer, saturating by the collimation of input waveguide 1, first being arranged in order in the z-direction
Mirror 2, the first balzed grating, 3, the second collimating lens 4, Fourier transform lens 5, the 3rd collimating lens 6, the second balzed grating, 7,
4th collimating lens 8, output waveguide 9 are constituted, and the material of each ingredient is identical, is non-crystalline silicon.
The annexation of each ingredient is：The input of the output end face of input waveguide 1 and the first collimating lens 2
Face is connected as a single entity, and the input end face of the output end face of the first collimating lens 2 and the first balzed grating, 3 is not contacted, and first glares
The input end face of the output end face of grid 3 and the second collimating lens 4 is not contacted, the output end face of the second collimating lens 4 and Fourier
The input end face of transform lenses 5 is not contacted, the input end face of the output end face of Fourier transform lens 5 and the 3rd collimating lens 6
Do not contact, the input end face of the output end face of the 3rd collimating lens 6 and the second balzed grating, 7 is not contacted, the second balzed grating, 7
The input end face of output end face and the 4th collimating lens 8 is not contacted, the collimating lens, glittered grating and Fourier transformation it is saturating
The top surface of mirror is same level, and the output end face of the 4th collimating lens 8 and the input end face of output waveguide 9 are connected as a single entity.
In addition to input waveguide 1, output waveguide 9 are respectively as transmitting and receiving terminal, the present invention is functionally divided into part A
(being made up of the first collimating lens 2, the first balzed grating, 3 and the second collimating lens 4), part B (Fourier transform lens 5) and C
Three parts partly (are made up of) the 3rd collimating lens 6, the second balzed grating, 7 and the 4th collimating lens 8.These planar waves spread out
Emitter part can be made on the substrate being made up of same material using unified photoetching and etching technics, and light is in vertical direction
All the time it is the slab waveguide structures guiding being made up of covering 12 and upper ducting layer 10, lower ducting layer 11.Part A is located at input
After fiber waveguide 1, its effect is to obtain the Fourier transformation of input time pulse in output spatial domain；The effect of part B is to A portions
Spatial fourier transform is done in the output for dividing；The effect of C portion is that the Fourier for obtaining the spatial distribution of part B output in time domain becomes
Change, the time pulse shape for finally exporting is the Fourier transformation of input time pulse.The present invention mass action be exactly
Input waveguide 1 is input into a ultra-short Time pulse, after the time domain Fourier transformer, in the time that output waveguide 9 is obtained
The shape of pulse is the time domain Fourier transformation of input time pulse.
Light in input waveguide 1 initially enters the first collimating lens of part A, and in Y-Z plane almost plane ripple is obtained,
After the first balzed grating, the light of different frequency component is focused onto the diverse location of the second collimating lens back focal plane, in
The spatial distribution for being part A output is exactly the Fourier transformation of input time pulse；The effect of part B is that part A is exported
Spatial distribution does spatial fourier transform, and the space field distribution of output is the shape of the time pulse from input waveguide input；C
Part is fully equivalent to part A reversion and is placed on after part B, according to principle of reciprocity, the time domain of the time pulse of C portion output
Shape is the Fourier transformation for input space distribution.The shape of the output time pulse that finally we obtain is input time
The Fourier transformation of pulse, therefore complete the function that Fourier transformation is realized in time domain.
Light pulse is incident from input waveguide 1, receives in output waveguide 9.The input waveguide 1 and output waveguide 9 are water
The cuboid of plane section rectangle, its size is：0.04 micron of x directions height, 2 microns of y directions width, z directions length is 10 micro-
Rice.
First collimating lens 2, the 3rd collimating lens 6 play the role of to collimate light, and in its focal plane directional light is obtained.
Second collimating lens 4, the 4th collimating lens 8 play the role of to focus on light, and in its focal plane focal beam spot is obtained.
First collimating lens 2, the second collimating lens 4, the 3rd collimating lens 6, the 4th collimating lens 8 are flat post
Body.The flat cylinder is made up of the two parts being connected as a single entity, as shown in figure 3, wherein：Part I horizontal cross sectional geometry is square
Shape, its size is：1 micron of x directions height, 207 microns of y directions width, 296 microns of z directions length.
Part II horizontal cross sectional geometry is half elliptic, and its major axis a and short axle b meet respectively：
In formula：nH(total equivalent of ducting layer, lower ducting layer, covering and substrate is gone up for the equivalent refractive index value in lens
Refractive index) it is 3.4；nLIt is 3.22 for the inner effective refractive index value of background material system (including lower ducting layer, covering and substrate)；nH
And nL(Mode solver) can be solved by Effective Index Method (Effective Index Method) or pattern to obtain.f
It it is 628 microns for the focal length value of lens.
First balzed grating, 3 plays a part of light splitting, and the light of different frequency has different yawing moments after grating, most
The light of different frequency component is focused on eventually the diverse location of the focal plane of the second collimating lens 4.That is, back focal plane
Spatially the light field of each point corresponds to each spectrum component of incidence wave.The effect of the second balzed grating, 7 is dodged with first
The effect contrast of credit grating 3, the light of all frequency components that different directions are propagated is changed into what is propagated in the same direction
Directional light.
First balzed grating, 3, the second balzed grating, 7 by 65 identical right-angle prismatic posts in the y-direction according to
Secondary close-packed arrays, as shown in figure 4, its size is：In the y-direction the length of side is 7.7 microns, and in the z-direction the length of side is 3.8 microns, x directions
Highly it is 1 micron.
The effect of Fourier transform lens 5 is to carry out spatial fourier transform, and behind focal plane obtains the sky of input field
Between Fourier transformation.The Fourier transform lens 5 is flat cylinder, and its cross section is as shown in figure 5, by two ends identical circular arc
Surround, arc radius are 190 microns, in the y-direction width is 230 microns.
The x, y, z direction be respectively along paper vertically upward, vertical paper outward direction, along paper to the right
To.
The above-mentioned optical time domain Fourier transformer that the present invention is provided, with optical time domain Fourier transformer traditional before
Compare, it is with the obvious advantage：The present invention is based on Planar Lightwave Circuit Technology, can be by any dielectric material reality that can form planar optical waveguide
It is existing, it is compatible with existing processing technology, can be made by the standard lithographic of Planar waveguide technology and etching technics, small volume, and can be square
Just the device of material system identical with other carries out single-chip integration.
Jing analog simulations are tested, and its result is as follows：
Used as input optical pulse, pulse width is 65fs to the Gaussian pulse that a centre wavelength is chosen for 1550nm, is used
Time domain beam propagation ratio (TD-BPM) is emulated to device, after the optical time domain Fourier transformer, last output
As shown in fig. 6, solid line represents the output result of emulation, dotted line represents the preferable Fourier of input pulse time waveform to pulse shape
Conversion, it can be seen that simulation result is basically identical with preferable Fourier transformation waveform, realizes time domain Fu to input pulse
In leaf transformation function.
Then, as shown in fig. 7, selecting centre wavelength 1550nm, pulse width is respectively two of 30fs and 90fs this height
Pulse emulates the output result for obtaining as shown in figure 8, solid line is the input pulse that pulse width is 30fs as input optical pulse
Output waveform, dotted line be pulse width for 90fs input pulse output waveform.As can be seen from the figure input pulse width
Degree is narrower, and its output pulse is wider, and this is narrower with time domain waveform, and the wider practical situation of its frequency spectrum is consistent, therefore
Can be used to realize the function of pulse stretching or compression.
Claims (7)
1. a kind of optical time domain Fourier transformer, is characterized in that by the covering grown successively from bottom to top on substrate (13)
(12), lower ducting layer (11) and upper ducting layer (10) are constituted；The upper ducting layer (10) is graph layer, by arranging successively in the z-direction
The input waveguide (1) of row, the first collimating lens (2), the first balzed grating, (3), the second collimating lens (4), Fourier transformation are saturating
Mirror (5), the 3rd collimating lens (6), the second balzed grating, (7), the 4th collimating lens (8), output waveguide (9) are constituted.
2. optical time domain Fourier transformer according to claim 1, is characterized in that the optical time domain Fourier transformer
Based on Planar Lightwave Circuit Technology, by the media implementation that can form planar optical waveguide, and by the standard light of Planar waveguide technology
Carve and etching technics makes, realization carries out single-chip integration to device.
3. optical time domain Fourier transformer according to claim 1, is characterized in that the substrate (13) by can be formed
The dielectric material of planar optical waveguide is made, and the material includes monocrystal silicon, indium phosphide, GaAs, sapphire or carborundum.
4. optical time domain Fourier transformer according to claim 1, is characterized in that the covering (12) by can be formed
The dielectric material of planar optical waveguide is made, and the material includes silicon dioxide, indium phosphide, InGaAsP, GaAs, aluminum gallium arsenide, nitrogen
Change gallium, indium gallium nitrogen or aluminum gallium nitride.
5. optical time domain Fourier transformer according to claim 1, it is characterized in that the upper ducting layer (10) and under lead
Ripple layer (11) employing can form the dielectric material of planar optical waveguide, the material include non-crystalline silicon, InGaAsP, GaAs,
Gallium nitride, indium gallium nitrogen or aluminum gallium nitride.
6. in claim 1 to 5 optical time domain Fourier transformer described in any claim purposes, it is characterized in that the optics
When time domain Fourier transformer is applied in ultrashort light pulse communication system, in time domain Fu to input time pulse can be realized
Leaf transformation function.
7. purposes according to claim 6, when it is characterized in that applying, comprises the following steps：
A. light pulse is incident from input waveguide (1), receives in output waveguide (9)；
B. the first collimating lens (2), the 3rd collimating lens (6) play the role of to collimate light, and in its focal plane directional light is obtained；
C. the second collimating lens (4), the 4th collimating lens (8) play the role of to focus on light, and in its focal plane focal beam spot is obtained；
D. first balzed grating, (3) plays a part of light splitting, and the light of different frequency has different deflection sides after grating
To finally the light of different frequency component being focused on the diverse location of the focal plane of the second collimating lens (4)；Second balzed grating,
(7) effect and the effect contrast of the first balzed grating, (3), the light of all frequency components of different directions propagation is changed into
The directional light propagated in the same direction；
E. the effect of the Fourier transform lens (5) is to carry out spatial fourier transform, and behind focal plane obtains input field
Spatial fourier transform.
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