CN102519584B - Monolithic integrated orthogonal balanced light detector - Google Patents

Abstract

The invention provides a monolithically integrated orthogonal balanced light detector, which includes two double balanced polarized light detectors capable of detecting TE and TM polarized light and a bias circuit thereof. The quadrature balanced optical detector can be used as a core component of a quadrature balanced receiver to detect QPSK/DQPSK signals. Also integrated in the device is a bias circuit including on-chip capacitors, high-frequency choke resistors, and load resistors. Because the detector has optical signal polarization selectivity, it does not need to use a polarization beam splitter, which can greatly reduce the volume of the optical receiver and improve the working speed and reliability of the device.

Description

Monolithic Integrated Quadrature Balanced Photodetector

technical field

The invention relates to the field of coherent detection, in particular to a single-chip integrated orthogonal balanced light detector, which includes two double balanced polarized light detectors capable of detecting TE and TM polarizations. The monolithic integrated quadrature balanced optical detector can be used as a core device of a quadrature balanced receiver to detect QPSK/DQPSK signals.

Background technique

The current receiving system of optical communication is divided into two categories: one is intensity modulation/direct detection (IM/DD); the other is coherent detection. Compared with IM/DD, coherent detection has higher detection sensitivity, smaller transceiver antenna aperture, lower power consumption, stronger anti-interference ability and higher speed. Therefore, coherent detection has become an important technical approach to develop a new generation of high bit rate, miniaturized and low power consumption space laser communication terminals.

As the core device of coherent detection, balanced detectors have attracted much attention and are widely used in space laser communication systems. At the same time, the application of balanced detectors in high-speed digital communication systems has gradually aroused people's interest, and can be applied to new modulation patterns based on stable and reliable link performance, such as differential phase-shift keying (QPSK), Differential Quadrature Phase Shift Keying (DQPSK), etc. In digital communication systems, this phase-sensitive encoding and transmission technology will become a trend, which can greatly increase the data transmission capacity, and the detection sensitivity and spectrum efficiency are the keys to this trend.

In coherent detection, the signal beam is required to be coherent with the local oscillator laser beam and have the same polarization direction in order to obtain the high sensitivity that coherent reception can provide. Because in this case, only the projection of the signal light wave electric vector in the direction of the local oscillator light wave electric vector can really contribute to the intermediate frequency signal current generated by frequency mixing. In order to give full play to the superiority of coherent reception, optical polarization stabilization measures should be taken in coherent optical communication. There are mainly three methods as follows: One is to use an optical polarization controller at the front end of the receiver, but this is at the cost of losing the power of the received signal. The second is to keep the polarization state of the light wave unchanged during the transmission process. For coherent optical fiber communication systems, since the ordinary single-mode optical fiber will change the polarization state of the light wave due to factors such as mechanical vibration or temperature changes of the optical fiber, "polarization-maintaining fiber" is usually used to achieve the same polarization state of the light wave during transmission. . However, compared with single-mode fiber, "polarization-maintaining fiber" has larger loss and is more expensive, so it is difficult to apply to long distances. For space optical communication, it is difficult to keep the polarization state of light waves unchanged during transmission. The third is to use the so-called orthogonal balance detection technology, which uses ordinary single-mode fiber or space for optical transmission. After the signal light at the receiving end is mixed with the local oscillator light, it is first divided into two paths for balanced reception, and polarization is used for each path. The beam splitter divides the two signals of orthogonal polarization into balanced detection respectively, and finally judges the two balanced received signals, and selects the better one as the output signal. The output signal at this time has nothing to do with the polarization state of the received signal, thereby eliminating the random change of the polarization state of the signal during transmission. The introduction of quadrature balance detection technology greatly improves the practicability of coherent detection technology.

The balanced detectors currently used in coherent detection technology are all based on discrete detectors, which have the disadvantages of large size, low stability and high cost. Similar to the large-scale integration of many transistors in the field of microelectronics to achieve complex functions and reduce costs, optoelectronic devices integrating multiple functions have also become a development trend, which is one of the key factors for reducing application system costs, reducing system volume and enhancing system stability. one. Figure 1 is a common quadrature balanced optical receiver, which consists of a 90° optical hybrid and two double-balanced optical detectors. advanced features. Moreover, this balanced optical receiver requires the use of a birefringent crystal polarization beam splitter, and the detector is usually based on III-V or IV materials, which is particularly unfavorable for integration. Therefore, we propose a new quadrature balanced receiver. In this structure, we replace the ordinary polarization-insensitive photodetector with a novel structure of polarized photodetector. Therefore, there is no need to use a large-volume polarization beam splitter, and the 90° optical hybrid can use a 2×4 multimode interferometer (MMI) based on semiconductor materials, and the orthogonal optical receiver can be integrated to greatly reduce the device volume , Improve device stability and reduce costs.

Contents of the invention

The present invention is made to solve the above-mentioned problems in the prior art, and its purpose is to provide an orthogonally balanced photodetector that can realize integration, greatly reduce the volume of the device, improve the stability of the device and reduce the cost.

In order to achieve the above-mentioned purpose of the invention, an orthogonally balanced photodetector related to the present invention is composed of a monolithic integration method, and is characterized in that it includes: more than two double-balanced orthogonally polarized photodetectors, respectively composed of two TE polarized A light detector or two TM polarized light detectors; and a bias circuit, including multiple on-chip capacitors, multiple AC isolation resistors and multiple load resistors.

In addition, it may be preferred that the substrate is a semi-insulating substrate, and all device materials are formed on the same substrate through vapor phase epitaxy or molecular beam epitaxy.

In addition, it may be preferable that both the TE polarized light detector and the TM polarized light detector are plane-incidence detectors.

In addition, it may be preferable to fabricate a high-contrast submicron dielectric grating or a metal (gold, silver, aluminum, germanium, etc.) grating on the incident surface to realize the polarization selectivity of the probe light.

In addition, it may be preferred that the design parameters of the detector gratings within the same double-balanced detector are the same.

In addition, it may be preferred that the high-contrast dielectric grating and metal grating have a wide reflection bandwidth and polarization selectivity for polarized light.

In addition, it may be preferable that the grating direction of the TM polarized light detector is perpendicular to the grating direction of the TE polarized light detector.

In addition, it may be preferred that when a dielectric grating is used, the ratio of the responsivity of the detector to TM and TE light is greater than 20 dB.

In addition, it may be preferred that the material of the metal grating is gold, silver, aluminum or germanium, and the ratio of the responsivity of the detector to TM and TE light is greater than 30 dB.

In addition, it may be preferable that the material of the metal grating is the same as that of the detector electrodes, and an insulating layer of 20-50 nm for electrical isolation is formed between the metal grating and the surface of the detector.

In addition, it may be preferred that the on-chip capacitor is used as a bias bypass capacitor, the structure of the on-chip capacitor is a metal-insulator-metal (MIM) structure, and the capacitance value of the on-chip capacitor is greater than 2pF.

In addition, it may be preferable that the isolation resistor and the load resistor use the same thin film resistor.

The present invention uses a polarized light detector (for avoiding confusion, the polarized detector referred to here is classified according to the polarization state of the light that can be detected by the detector, for example, if the detector can only detect TE (transverse electric field Wave) polarized light, we call it TE polarized light detector, similarly TM (transverse magnetic field wave) polarized light detector can only detect TM polarized light as the core device of the orthogonal receiver, two double-balanced detectors can only To detect TE and TM polarized signals, we integrate a bias circuit in this device, including on-chip capacitors, high-frequency containment resistors and load resistors. Since the detector has polarization selectivity for optical signals, it does not need to use a polarizing beam splitter , can greatly reduce the volume of the optical machine receiver, and improve the working speed and reliability of the device.

Regarding the concepts of TE mode and TM mode, for a uniform planar electromagnetic wave propagating in free space (there is no free charge in the space, no conduction current), the electric field and magnetic field have no components parallel to the direction of wave propagation, and are perpendicular to the direction of propagation. At this time, the electric vector E, the magnetic vector H and the propagation direction k are perpendicular to each other, and the electromagnetic wave is a transverse wave. The electromagnetic wave propagating along a certain path (such as a waveguide) is a guided electromagnetic wave. According to Maxwell's equations, guided electromagnetic waves generally have E and H components in the direction of propagation.

From the perspective of the classification of light propagation forms: according to whether there is an electric field component or a magnetic field component in the direction of propagation, it can be divided into three types: TEM wave, TE wave and TM wave. Any light can be expressed in the form of the synthesis of these three waves.

1. TEM wave: There is no electric field and magnetic field component in the direction of propagation, called transverse electromagnetic wave. The actual laser mode is a quasi-TEM mode, which allows the existence of Ez and Hz components, but they must << the transverse component, because a larger Ez means that the direction of the wave vector deviates from the optical axis, and it is easy to overflow out of the cavity, so the loss is large , it is difficult to form an oscillation.

2. TE wave (that is, the s wave in the object light): there is a magnetic field component but no electric field component in the direction of propagation, and it is called a transverse electric wave. In the planar optical waveguide (closed cavity structure), the electromagnetic field components have Ey, Hx, Hz, and the propagation direction is the z direction.

3. TM wave (that is, the p wave in the object light): there is an electric field component but no magnetic field component in the direction of propagation, and it is called a transverse magnetic wave. In the planar optical waveguide (closed cavity structure), the electromagnetic field components include Hy, Ex, and Ez, and the propagation direction is the z direction.

The quadrature balanced receiver proposed by the present invention has an equivalent circuit diagram of its devices as shown in Figure 2, PD1 and PD2 are TE polarized light detectors with the same device structure, forming a TE polarization double-balanced detector; PD3 and PD4 are the same device Structured TM polarized light detection constitutes a TM polarized double-balanced detector. C is an on-chip capacitor, R is a thin film resistor (or AC isolation resistor), C and R form a Bias-T-like function, Rload is a 100Ω load resistor, and Vcc is a DC bias voltage.

The structure of the integrated device is shown in Figure 3. The photodetector is a surface-incidence detector, and the signal light is incident vertically on the upper surface of the photodetector. The detector can be a PIN detector, an avalanche detector (APD) or a single row carrier Detector (UTC-PD), etc. The material structure can be based on Group III-V or Group IV materials or a mixture of the two, such as InP/InGaAsP materials, InP/InGaAlAs materials, GaAs/AlGaAs, GeSi/Si and GaAs/Ge, etc. The electrode structure of the detector is a coplanar strip (CPS) structure, the characteristic impedance of the input end is 50 ohms, and the modulation bandwidth of the device is greater than 40 GHz. The detector has polarization selectivity for absorbing light, which can be realized by using a high-contrast submicron dielectric grating or a metal (gold, silver, aluminum, germanium, etc.) grating on the surface of the device. By designing parameters such as the period, height and duty cycle of the grating, photodetectors sensitive to TE and TM polarized light can be realized respectively. The detector grating design parameters within the same double-balanced detector are the same.

On-chip capacitors are widely used in the MMIC (Monolithic Microwave Integrated Circuit) process, and have the advantages of small size and compatibility with semiconductor processes. In monolithic integrated quadrature balanced detector applications, we use it as a bias bypass capacitor, its structure and metal - insulating layer - metal (MIM) structure. By designing the area of the metal layer, the thickness and area of the insulating layer, different capacitance values can be realized.

Both the AC isolation resistor and the load resistor in the integrated device are composed of thin film resistors compatible with the CMOS process, and its structure is rectangular, and different resistance values can be achieved by changing the aspect ratio. The resistance value of the AC isolation resistor is generally greater than 1000 ohms, and is used to isolate the influence of the AC signal detected by the detector on the DC bias voltage source. The material of the thin film resistor is Ta ₂ N or AuCr, etc., which can be realized by electron beam evaporation combined with lift-off and other processes to form a thin film.

To avoid electrical crosstalk, isolation trenches are used between TE and TM double-balanced detectors, as shown in Figures 7 to 10. Between the TE detectors and between the TM detectors, an isolation trench and an insulating layer are used to realize the isolation of the N electrodes, as shown in FIGS. 6 to 10 .

Although the present invention will be described below in conjunction with some exemplary implementations and usage methods, those skilled in the art should understand that the present invention is not intended to be limited to these embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

Other advantages, objects and features of the present invention will be set forth in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the investigation and research below, or can be obtained from It is taught in the practice of the present invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Description of drawings

Fig. 1 is the schematic diagram of existing quadrature balanced receiver, wherein BPD is quadrature balanced detector;

Fig. 2 is the equivalent circuit diagram of the monolithic integrated quadrature balanced detector involved in the present invention;

Fig. 3 is the overall structural diagram of the monolithic integrated quadrature balanced detector involved in the present invention;

Fig. 4 is the overall structural diagram of the monolithic integrated quadrature balance detector involved in the present invention, 1-6 correspond to different positions;

Fig. 5 is a sectional view at position 1 of Fig. 4;

Fig. 6 is a sectional view at position 2 of Fig. 4;

Fig. 7 is a sectional view at position 3 of Fig. 4;

Fig. 8 is a sectional view at position 4 of Fig. 4;

Fig. 9 is a sectional view at position 5 of Fig. 4;

Fig. 10 is a sectional view at position 6 of Fig. 4;

FIG. 11 is a schematic structural diagram of an on-chip capacitor;

Fig. 12 is a schematic view showing the structure of a diffraction grating and the definition of TE/TM polarization;

Figure 13 shows the reflection-transmission spectrum of the InGaAs (n=3.4) dielectric grating, Figure 13(a) shows the case where the incident light is TE polarized light, Figure 13(b) shows the case where the incident light is TM polarized light, in addition, the grating The period is p=1.1μm, the thickness of InGaAs is h=0.25μm, and the duty ratio is 0.35;

Fig. 14 is a schematic diagram of a surface-incident detector representing a dielectric grating, and the grating parameters are the same as those in Fig. 13;

Figure 15 shows the reflectance-transmission spectrum of the detector, Figure 15(a) shows the case where the incident light is TE polarized light, and Figure 15(b) shows the case where the incident light is TM polarized light, here, the detector is assumed to be in the whole The absorption coefficient of the band is 0;

Figure 16 is a schematic diagram of a surface incidence detector showing a metallic (Au) grating;

Fig. 17 shows the calculated TE/TM reflection-transmission spectrum of the metal grating, where the grating period is p=0.45 μm, the gold thickness h=0.5 μm, and the duty ratio is 0.35.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further elaborated below in combination with specific examples and with reference to the accompanying drawings.

Figure 1 is a schematic diagram of an existing quadrature balanced receiver, which consists of a 90° optical mixer and two double-balanced photodetectors. advanced features. This balanced optical receiver requires the use of birefringent crystal polarizing beam splitters, and detectors are usually based on III-V or IV materials, which is particularly unfavorable for integration.

The monolithically integrated orthogonally balanced optical detector proposed in the present invention integrates two double-balanced orthogonally polarized optical detectors and their bias circuits, which can greatly reduce the volume of the orthogonally balanced receiver and improve the performance of the receiver. stability and reduce its cost. Fig. 3 is an overall structure diagram of the monolithic integrated quadrature balanced detector involved in the present invention. The integrated device includes two TE polarized light detectors 4 , two TM polarized light detectors 6 , four on-chip capacitors 12 , two AC isolation resistors 9 and four 100-ohm load resistors 14 . Among them, 1 is the substrate, including semi-insulating substrate material and N or P buffer layer, which can be Si, Ge, GaAs or InP and other IV or III-V materials, and the surface resistance of the semi-insulating substrate is 106-108Ω. cm, the semi-insulating substrate is generally achieved by doping Fe, and the thickness of the substrate layer is between 50 and 600 μm; the N or P-type buffer layer is the same material as the semi-insulating substrate, and the doping concentration is generally 1018 ～1019cm ^-3 , thickness 50nm～2μm. For example, if the semi-insulating substrate material is InP, the N or P-type buffer layer is also InP. 2 is the P or N electrode of the TE polarization detector 1 (if the buffer layer on the substrate is N-type doped, then 2 is the P electrode of the TE detector; if the buffer layer on the substrate is P-type doped, then 2 is the N electrode of the TE detector. The letters before and after the word "or" correspond to each other, and the following writing methods are the same). 3 is the N or P electrode of TE polarization detector 2, 4 is the P or N electrode of TE polarization detector 2, 5 is the P or N electrode of TM polarization detector 1, 6 is the P or N electrode of T polarization detector 2 Electrode, 7 is SiO2 or SiNx insulating layer, 10 is DC bias voltage electrode, 11 is the N or P electrode of TM polarization detector 2, 12 is on-chip capacitor, 13 is the N or P electrode of TM polarization detector 1, 15 is the N or P electrode of the TE polarization detector 1, and 16 DC bias voltage electrodes. The material structure of the entire device can be obtained by a single MOVPE or MBE material.

5 to 10 are cross-sectional views at positions 1 to 6 in FIG. 4, respectively. Figure 11 is a schematic diagram of the on-chip capacitor, which includes a metal-insulating layer-metal structure. The metal can be the N electrode or P electrode of the detector, and the insulating layer material in the middle is SiO2, SiNx, BCB, polymide, etc. Materials with good insulation and high dielectric constant are conducive to the formation of on-chip capacitors with high capacitance values. For our integrated devices, the capacitance value is generally greater than 2pF. If the semi-insulating substrate is InP or GaAs material, the N electrode can be AuGeNi alloy, AuTi alloy, AuPtTi alloy or AuPdTi alloy, etc., and the P electrode can be AuZn alloy, AuCr alloy, AuTi alloy, AuPtTi alloy or AuPdTi alloy, etc. When the electrode area is 6*10-9m2, the insulating layer is SiO2, and its thickness is not greater than 100nm, the capacitance value of the on-chip capacitor is greater than 2pF.

The detector has polarization selectivity for absorbing light, which can be realized by using a high-contrast submicron dielectric grating or metal (gold, silver, aluminum, germanium, etc.) grating on the surface of the device. The submicron dielectric grating or metal grating has high Polarization dependent, wide reflection bandwidth. Figure 12 is a schematic diagram of a diffraction grating. The definition of TE or TM polarization is shown in the figure. The so-called high contrast refers to the large difference in refractive index between the grating material and the filling material around the grating. The filling material around the grating shown in Figure 12 is air. . Figure 13 is the calculated reflection and transmission spectra of the InGaAs (n=3.4, h=0.25) dielectric grating surrounded by air, with a period of 1.1 μm and a duty ratio of 0.35. It can be seen from the figure that the grating has a reflectivity of nearly 100% for TE polarized light and close to 0% for TM polarized light in the C-band of the entire communication wavelength. It has high polarization selectivity and can be applied to TM polarization detection. device.

Next, we take InP material as an example to illustrate the structural diagram of the TM polarization detector device. As shown in Figure 14, material 1 is P-type doped InGaAs, which is not only the contact layer of the detector, but also the grating layer.

Material 2 is an InP confinement layer, which is also used as a sacrificial layer of the grating, and can be released by a selective etching solution. The thickness of InP is about 350nm. 3 is the remaining material structure of the detector (P-I-N or I-N). Taking the single row carrier detector as an example, its structure is P-InGaAs, I-InGaAsP and N-InP from top to bottom. Applying the grating parameters in Figure 13 to our device, we obtained the reflection and transmission spectra of TE and TM polarized light as shown in Figure 15. In the calculation, we assume that the detector is transparent to the entire light, and it can be seen that in the entire communication wavelength C-band, the transmittance of TE polarized light is close to 100%, while the transmittance of TM polarized light is greater than 60%, with high polarization selective. If the absorption of the detector is 100cm-1, the ratio of the photoresponsivity of the detector to TM and TE is greater than 20dB. For TE polarization detectors, we can achieve this by adjusting the grating period and duty cycle. A simple approach is that we use the grating design parameters of the TM polarization detector as described above, the difference is that the grating direction is rotated 90° clockwise or counterclockwise.

For the metal grating, its structure is shown in Figure 16. The metal grating is located on the surface of the detector. In order to prevent electrical crosstalk, a layer of SiO ₂ or SiNx insulating layer can be deposited on the semiconductor surface before depositing the metal grating. The material of metal grating can be gold, silver, aluminum and germanium etc. Figure 17 is the calculated transmission spectrum of a gold (h=0.5) grating with a period of 0.45 μm and a duty ratio of 0.35. It can be seen from the figure that the grating has a transmittance difference of more than 30dB between TM and TE polarized light in the entire communication wavelength C-band, and can be applied to TM polarized detectors. For TE polarized detectors, the method described above for dielectric gratings can also be used.

To avoid electrical crosstalk, isolation trenches are used between TE and TM double-balanced detectors, as shown in Figures 7 to 10. Between the TE detectors and between the TM detectors, an isolation trench and an insulating layer are used to realize the isolation of the N electrodes, as shown in FIGS. 6 to 10 .

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent replacements without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the claims of the present invention.

Claims (12)

1. an orthogonal balanced light detector, is constituted in single-chip integration mode, it is characterised in that including:

2 double flat weighing apparatus cross-polarization photo-detectors, the first double flat weighing apparatus cross-polarization photo-detector is by a TE Polarized light detector and the 2nd TE polarized light detector are constituted, the second double flat weighing apparatus cross-polarization photo-detector It is made up of a TM polarized light detector and the 2nd TM polarized light detector；And

The biasing circuit of described double flat weighing apparatus cross-polarization photo-detector, has four on-chip capacitance, four friendships Stream isolation resistance and four load resistances,

Wherein, described double flat weighing apparatus cross-polarization photo-detector and described biasing circuit share same substrate, and And described double flat weighing apparatus cross-polarization photo-detector also includes P metal electrode and N metal electrode, described first The P metal electrode of the N metal electrode of TE polarized light detector and described 2nd TE polarized light detector by Same electrode is formed, the N metal electrode of a described TM polarized light detector and described 2nd TM The P metal electrode of polarized light detector is formed by same electrode, described first double flat weighing apparatus crossed polarized light Electric isolation between detector and described second double flat weighing apparatus cross-polarization photo-detector；

One end of first exchange isolation resistance connects the P metal electrode of a described TE polarized light detector Being simultaneously connected with one end of the first on-chip capacitance, it is inclined that the other end of described first exchange isolation resistance connects direct current Put the negative pole of voltage；One end of second exchange isolation resistance connects described 2nd TE polarized light detector N metal electrode also connects one end of the second on-chip capacitance, and the other end of described second exchange isolation resistance is even Connect the positive pole of described DC offset voltage；One end of first load resistance connects described first on-chip capacitance The other end, the other end of described first load resistance connects a described TE polarized light detector and described The same electrode that 2nd TE polarized light detector is formed；One end of second load resistance connects described the The other end of two on-chip capacitance, the other end of described second load resistance also connects a described TE polarization The same electrode that photo-detector and described 2nd TE polarized light detector are formed；And

One end of 3rd exchange isolation resistance connects the P metal electrode of a described TM polarized light detector Being simultaneously connected with one end of the 3rd on-chip capacitance, the other end of described 3rd exchange isolation resistance connects another The negative pole of DC offset voltage；One end of 4th exchange isolation resistance connects described 2nd TM polarized light and visits Surveying the N metal electrode of device and connect one end of the 4th on-chip capacitance, the described 4th exchanges the another of isolation resistance One end connects the positive pole of another DC offset voltage described；One end of 3rd load resistance connects described the The other end of three on-chip capacitance, the other end of described 3rd load resistance connects a described TM polarized light The same electrode that detector and described 2nd TM polarized light detector are formed；The one of 4th load resistance End connects the other end of described 4th on-chip capacitance, and the other end of described 4th load resistance also connects described The same electrode that oneth TM polarized light detector and described 2nd TM polarized light detector are formed.

Orthogonal balanced light detector the most according to claim 1, it is characterised in that substrate is the most absolutely Edge substrate, all device materials are the most on the same substrate through a vapour phase epitaxy or molecular beam epitaxy Formed.

Orthogonal balanced light detector the most according to claim 1, it is characterised in that described TE is inclined Shake photo-detector and described TM polarized light detector is face incidence detector.

Orthogonal balanced light detector the most according to claim 2, it is characterised in that by incidence Surface makes submicron dielectric grating or the metal grating of high-contrast, it is achieved the polarization choosing to detection light Select characteristic.

Orthogonal balanced light detector the most according to claim 2, it is characterised in that same double flat weighs Detector Grating Design parameter in detector is identical.

Orthogonal balanced light detector the most according to claim 2, it is characterised in that high-contrast Dielectric grating and metal grating possess wide reflection bandwidth and polarization selectivity to polarized light, wherein, with InGaAs be grating material and with air as grating around packing material diffraction grating situation in, grating Cycle is 1.1 μm, and dutycycle is 0.35.

Orthogonal balanced light detector the most according to claim 2, it is characterised in that TM polarizes The grating orientation of photo-detector is vertical with the grating orientation of TE polarized light detector.

Orthogonal balanced light detector the most according to claim 2, it is characterised in that use medium light During grid, described TM, TE polarized light detector is more than 20dB to the ratio of the responsiveness of TM, TE light.

Orthogonal balanced light detector the most according to claim 2, it is characterised in that metal grating Material is gold, silver, aluminum or germanium, described TM, TE polarized light detector responsiveness to TM, TE light Ratio more than 30dB.

Orthogonal balanced light detector the most according to claim 2, it is characterised in that metal grating Identical with the material of described TM or TE polarized light detector electrodes, at metal grating and described TM or The insulating barrier of be used for electric isolution 20～50nm is formed between the surface of TE polarized light detector.

11. orthogonal balanced light detectors according to claim 1, it is characterised in that on described Electric capacity is as biasing shunt capacitance, and the structure of this on-chip capacitance is metal-insulator-metal (MIM) knot Structure, the capacitance of on-chip capacitance is more than 2pF.

12. orthogonal balanced light detectors according to claim 1, it is characterised in that described isolation Resistance uses identical film resistor with load resistance.