Rectangular, micro annular resonant cavity type light filter
One, technical field
The invention belongs to the integrated optics technique field, relate to a kind of waveguide type optical filter that is used for optical communication system, optical computer system and photon/optoelectronic integrated circuit, specifically a kind of rectangular, micro annular resonant cavity type light filter.
Two, background technology
Optical filter is the base components of optical communication system, optical computer system and photon/optoelectronic integrated circuit, does not have functions such as the monitoring of interruption in order to realize wavelength-division multiplex/demultiplexing, light top and bottom path, light signal.Optical filter mainly contains kinds such as grating type, interfere type, waveguide array grating type, optical fiber melting cone type and waveguide micro annular resonant cavity type.The grating type light filter wavelength scope of application is narrower, interfere type optical filter filtering channel number is few, and membraneous material moisture-sensitive and change its stability, waveguide array grating type optical filter is to temperature variation and polarization of incident light attitude sensitivity, and optical fiber melting cone type optical filter channel isolation is poor.More than four kinds of optical filters be discrete component, be not easy to realize that with other photonic device monolithic is integrated.The waveguide micro annular resonant cavity type light filter has that volume is little, the quality factor advantages of higher, and is easily integrated with photonic device realization monolithics such as waveguide type modulator/switch, laser instrument, detectors.At present, the waveguide micro annular resonant cavity type light filter mainly adopts circular little ring structure, and the shortcoming of this structure is: 1, the difficulty of processing of circular little ring is big, and brings scattering loss easily; The interaction of 2, circular little ring and input/go out passage is apart from weak point, and the spacing of thereby little ring and input/go out passage is little, further increases difficulty of processing, and the device yields is low; 3, the free spectral range of optical filter is little, is difficult for being applied in the secret letter wavelength division multiplexed optical network.
Three, summary of the invention
In order to overcome the deficiency of existing waveguide micro annular resonant cavity type light filter, the purpose of this invention is to provide a kind of rectangular, micro annular resonant cavity type light filter, this optical filter compact conformation, the processing technology difficulty is little, and free spectral range is big.
The objective of the invention is to be achieved through the following technical solutions:
A kind of rectangular, micro annular resonant cavity type light filter is characterized in that: it comprises highway and rectangular, micro annular resonant cavity, and described rectangular, micro annular resonant cavity is joined end to end by four right-angle turning devices and constitutes; Introduce the multimode waveguide that is cut into 45 degree angles on the angle of right-angle turning device; Highway is positioned at the side of rectangular, micro annular resonant cavity, and the center section of highway and rectangular, micro annular constitute directional coupler.
Among the present invention, highway can be one, also can have two, only with a common-use tunnel, forms notch filter.When adopting two highways, left surface at rectangular, micro annular resonant cavity is provided with highway, right flank at rectangular, micro annular resonant cavity also is provided with highway, and the center section of two highways constitutes left side directional coupler and right side directional coupler with rectangular, micro annular resonant cavity respectively.
When adopting two highways, the termination of left side highway is respectively input channel 1a and put-through channel 1b; The termination of right side highway is respectively down paths 2a and last paths 2b.
According to different needs, rectangular, micro annular resonant cavity of the present invention can be that one dimension or two dimension series connection form higher order filter.
Rectangular, micro annular resonant cavity type light filter of the present invention is made up of rectangular, micro annular resonant cavity and highway.Wherein rectangular, micro annular resonant cavity is joined end to end by four right-angle turning devices and constitutes, highway is in the both sides of rectangular, micro annular resonant cavity, center section and rectangular, micro annular constitute two directional couplers, and all the other four ends are input channel, last paths, following paths and put-through channel.Introduce the multimode waveguides be cut into 45 degree angles on the angle of right-angle turning device, according to time domain coupled mode theory, but resonance wavelength no reflection events and radiationless be coupled to output waveguide from input waveguide realizes low-loss right-angle turning device.Multiple wavelength optical signal by the input channel input partly is coupled in the rectangular, micro annular resonant cavity through first directional coupler light field, and along the ring transmission, partly be coupled to output channel once more through second directional coupler light field, all the other light fields continue transmission along ring, are back to first directional coupler.The transmission and so forth of light letter.If light field and the input light field of this wavelength the phase differential that the odd-multiple of π arranged of certain wavelength signals after one week of ring transmission (many weeks), according to the interference of light principle, then both destructive interferences, by law of conservation of energy, this wavelength light field constructive interference of second directional coupler, therefore this wavelength is realized filter function from paths output down.Similarly, the wavelength light signal of constructive interference destructive interference in second directional coupler in a directional coupler, so this wavelength optical signals put-through channel output become straight-through light signal.
Compared with prior art, advantage of the present invention is: 1, compact conformation; Do not have curved waveguide, difficulty of processing is little, the yields height; 2, the mutual work district separation of directional coupler is long, increases distance between the two, further reduces difficulty of processing; 3, because right-angle turning device and rectangular, micro annular all have the frequency-selecting function, therefore free frequency spectrum encloses greatly, can be applicable in the secret letter wavelength division multiplexed optical network.
The mutual work district separation of directional coupler is long among the present invention, can reach 0.5~0.8 μ m, and the mutual work district separation of directional coupler is about 0.2 μ m in original optical filter, thereby difficulty of processing of the present invention is little.And free frequency spectrum of the present invention encloses greatly, can reach about 60nm, and original optical filter is at 1~10nm.Application of the present invention is wide.
Four, description of drawings
Fig. 1 is the structural representation that first example of the present invention has two highways.
Fig. 2 is the structural representation of right-angle turning device among the present invention.
Fig. 3 is the spectral characteristic figure of right-angle turning device among the present invention.
Fig. 4 is the optical field distribution figure of right-angle turning device when operation wavelength is 1.55 μ m among the present invention.
Fig. 5 is the spectral characteristic figure of first example of the present invention.
Fig. 6 is that first example of the present invention is the optical field distribution figure of 1.55 μ m in operation wavelength.
Fig. 7 is the structural drawing that second example of the present invention has a highway.
Fig. 8 is the structural drawing of the 3rd example of annular micro-ring resonant cavity optical filter.
Fig. 9 is the structural drawing of the 4th example of annular micro-ring resonant cavity optical filter.
Figure 10 is the structural drawing of the 5th example of annular micro-ring resonant cavity optical filter.
Description of reference numerals
1,11-highway 2-rectangular, micro annular resonant cavity 3-right-angle turning device
Directional coupler 6-right side, 4-directional coupler 5-left side directional coupler
8-input waveguide 9-output waveguide 10-45 degree angle multimode waveguides
Paths 2b-goes up paths under the 1a-input channel 1b-put-through channel 2a-.
Five, embodiment
Embodiment 1
Fig. 1 is first example of the present invention, has the structural representation of two highways.Wherein, highway 1 is in the left side, and highway 11 is on the right side, by input channel 1a, and following paths 2a, put-through channel 1b, last paths 2b, left side directional coupler 5, right side directional coupler 6, right-angle turning device 3 are formed.Multiple wavelength optical signal is imported from input channel 1a, through first left side directional coupler 5, part is exported by put-through channel 1b, remainder is coupled in the right-angle turning device 3 and transfers in second right side directional coupler 6, light signal part once more is coupled to down paths 2a output, and remainder is back in first left side directional coupler 5 through the device 3 that directly turns round.The transmission and so forth of light letter.If certain wavelength signals is back to the light field of first left side directional coupler 5 and this wavelength is had the odd-multiple of π by the input light field of input channel 1a phase differential after one week of ring transmission or many weeks, according to the interference of light principle, then both destructive interferences, by law of conservation of energy, this wavelength light field constructive interference of second right side directional coupler 6, therefore this wavelength is realized filter function from paths 2a output down.Similarly, wavelength light signal destructive interference in second right side directional coupler 6 of constructive interference in a left side directional coupler 5, so this wavelength optical signals put-through channel 1b output become straight-through light signal.Among the present invention, because entire device does not have curved waveguide, difficulty of processing is little; The mutual work district separation of directional coupler is long, increases distance between the two, further reduces difficulty of processing; Because right-angle turning device and rectangular, micro annular all have the frequency-selecting function, therefore free frequency spectrum encloses greatly.
Fig. 2 is the structural drawing of right-angle turning device 3, and Fig. 3 is the spectral characteristic of right-angle turning device 3, the optical field distribution of right-angle turning device 3 when Fig. 4 is 1.55 μ m for operation wavelength, and as seen this right-angle turning device has realized that low-loss 90 degree of light signal turn round.Fig. 5 is the frequency characteristic of this example, the optical field distribution when Fig. 6 is 1.55 μ m for operation wavelength, as seen this device has been realized filter function, and free frequency spectrum to enclose model big.
Embodiment 2
Fig. 7 is second example of the present invention.Only, promptly have only input channel 1a and put-through channel 1b, constitute notch filter with rectangular, micro annular resonant cavity and directional coupler with a highway 1.If light field and the input light field of this wavelength the phase differential that 2 π integral multiples arranged of certain wavelength signals after one week of ring transmission or the many weeks, according to the interference of light principle, then both destructive interferences, by coupled mode theory, if this moment, light signal equated with the straight-through coefficient of directional couple along the total losses in little one week of ring, then this wavelength is limited in transmission in little ring, can not export from the highway output terminal, realize trap function, so this device is a notch filter.
Embodiment 3
Fig. 8 is the 3rd example of the present invention.Adopt the series connection of two rectangular, micro annulars to constitute resonator cavitys, compare with first example, by light-transfer characteristic as can be known, the 2b exchange of setting out on a journey of following paths 2a and last paths, and can be extended to plural serial stage formation higher order filter, be used for improving the fineness of device.
Embodiment 4
Fig. 9 is the 4th example of the present invention.Adopt two rectangular, micro annular series connection to constitute resonator cavity, constitute notch filter, and can be extended to plural serial stage formation high-order notch filter, improve the fineness of device.
Embodiment 5
Figure 10 is the 5th example of the present invention.Adopt four rectangular, micro annular bidimensional series connection to constitute resonator cavity, this example increases the making tolerance of device, improves the fineness of device, and can be extended to plural serial stage formation higher order filter.