A kind of all-solid-state optical biological probe based on optical phased array principle

Abstract

The application discloses a kind of full solid-state optical biological probes based on optical phased array principle.The probe includes probe base and probe arm two parts, two parts are the full solid-state structure processed on the same silicon optical chip;The probe base includes input optical coupler, 1×n optical switch, n optical beam splitting modulation array and multiple electrical interfaces;The probe arm contains multiple sensing electrodes and n optical antenna array;Each optical structure of the probe is connected by single-mode waveguide or multiple single-mode waveguide, and each electrical structure is connected by copper metal layer wiring.The application can form quasi-Bessel beam under the condition that the radiation light of the optical antenna array meets the initial amplitude and initial phase condition, the quasi-Bessel beam has strong penetration in biological tissue, and two-dimensional deflection of pointing angle can be realized by adjusting phase, deflection speed is fast, and spatial resolution is high.

Description

Technical Field

[0001] This invention relates to an all-solid-state optical biological probe based on the principle of optical phased array, which can realize near-field quasi-Bessel beam shaping and two-dimensional scanning of beam emission angle, belonging to the interdisciplinary field of integrated optoelectronics and optogenetics. Background Technology

[0002] Optogenetics is a technique that combines genetic engineering and optical technology to precisely regulate specific cells in an organism. It works by converting specific neurons into light-sensitive channel proteins expressed on the cell membrane. When these proteins are stimulated by light of a specific wavelength, they open or close, altering the excitation or inhibition state of the nerve cell. These changes are reflected in variations in membrane potential, ion concentration, and biological behavior. By observing these phenomena, the physiological phenomena and mechanisms of the nervous system can be more clearly understood. This technique provides neuroscience research with a rapid and precise method to control the activity of single or clustered neurons, characterized by minimal side effects, high temporal and spatial resolution, and strong cell type specificity.

[0003] The development of precision optical probes is one of the core and challenging aspects of optogenetics. Traditional optical probes are typically based on in vitro focusing lenses, implanted tapered optical fibers, or implanted LEDs. With the development of on-chip optical integration technology and the increasing maturity of silicon and silicon nitride-based process platforms, more precise, complex, and reliable optical bioprobes based on micro- and nano-scale optical waveguide structures have become a research hotspot. Currently, a widely favored optical probe structure design involves introducing light from an external light source into an integrated waveguide via optical fiber, then using the integrated waveguide to process and guide the light into biological tissue to achieve optical stimulation. This type of optical probe overcomes the drawbacks of traditional optical probes, such as significant tissue damage and low precision. However, based on current research, existing optical bioprobes can only achieve fixed-point optical stimulation and discrete-point stimulation point switching. They cannot achieve high spatial resolution beam-focusing optical stimulation or more flexible and precise light emission angle switching and scanning with high temporal resolution. Summary of the Invention

[0004] To address the problems existing in the background technology, the present invention aims to provide an all-solid-state optical biological probe based on the principle of optical phased array. This probe can achieve variable focusing of near-field quasi-Bessel beams, as well as multi-dimensional, high-speed, and high-precision continuous beam pointing and scanning. The present invention achieves flexible beam angle scanning and near-field focusing distance control by rationally designing the amplitude distribution of each beam in the optical phased array and adjusting the phase distribution of each beam. It can also simultaneously adjust the shape of the emitted beam, thereby realizing an all-solid-state optical biological probe with high spatial and temporal resolution. This probe can form focused beams at different depths, orientations, and distances within biological tissues to stimulate neurons at specific locations within the tissues. Its application in optogenetics has significant scientific and practical value for understanding the structure and function of the human brain, the interaction between the human brain and the external environment, biomedicine, and brain-like computer science.

[0005] The technical solution adopted in this invention is:

[0006] A fully solid-state optical biological probe based on the principle of optical phased arrays is disclosed. The probe, according to its physical structure, can be divided into two parts: a probe base and a probe arm. Both parts are fabricated on the same silicon photonic chip, forming a fully solid-state structure.

[0007] The probe base, arranged sequentially according to the probe's optical path, includes an input optical coupler, a 1×n optical switch, and n optical beam splitter modulation arrays. The n optical beam splitter modulation arrays are identical in composition, and each array comprises an optical beam splitter, an amplitude modulation array, and a phase modulation array, arranged sequentially according to the optical path. The various structures on the probe base are connected sequentially via one or more single-mode waveguides according to the optical path. The probe base also includes multiple electrical interfaces for connecting to external electrical modules. These external electrical modules are a drive module and a signal processing module.

[0008] The probe arm includes multiple sensing electrodes and n optical antenna arrays; the n optical antenna arrays are identical in structure except for their positions on the probe arm; the optical input end of the optical antenna array is connected to the optical output end of the optical beam splitter modulation array in the probe base through multiple single-mode waveguides.

[0009] In the above technical solution, the input optical coupler is further described as an end-face coupler or a grating coupler, which serves as the optical interface of the probe and connects to an external optical fiber or laser. Its function is to couple external laser light onto the probe.

[0010] Furthermore, the 1×n optical switch has a single-ended optical input and n-ended optical output structure, and is composed of multiple 1×2 thermally modulated optical switches or electrically modulated optical switches cascaded together. Applying a voltage to the 1×n optical switch can control the input laser source to output from one or more of its output ports.

[0011] Furthermore, the optical beam splitting network in the optical beam splitting modulation array is composed of multiple 1×2 multimode interference couplers cascaded together, which is used to split one beam into multiple beams of equal power and output them to the amplitude modulation array.

[0012] Furthermore, the amplitude modulation array in the optical beam splitter modulation array is composed of multiple directional couplers arranged in parallel. By setting the coupling length of each directional coupler, multiple input beams with equal amplitude distribution can be modulated into multiple output beams with specific amplitude distribution.

[0013] Furthermore, the phase modulation array in the optical beam splitter modulation array is composed of multiple thermo-optical phase shifters or electro-optical phase shifters, and the phase of each output light is independently controlled by an external voltage;

[0014] Furthermore, the optical antenna array consists of multiple micro-waveguide grating antennas arranged in two orthogonal directions in a two-dimensional antenna array of N rows and N columns, through which on-chip lasers are radiated into the off-chip space.

[0015] Furthermore, the multi-channel output light with a specific amplitude distribution output from the amplitude modulation array satisfies the initial amplitude condition, which is the amplitude A of the radiated light from the microwaveguide grating antenna in the nth row and mth column of the optical antenna array. nm for:

[0016]

[0017] In the formula, N is the number of rows and columns of the optical antenna array; S is a positive coefficient less than or equal to 1.

[0018] Furthermore, by applying an initialization voltage to the phase shifter, the emitted light from the optical antenna array satisfies an initial phase condition, which is such that the phase Φ of the emitted light from the microwaveguide grating antenna in the nth row and mth column of the optical antenna array... n for:

[0019]

[0020] In the formula, N is the number of rows and columns of the optical antenna array, and Φ0 is a positive phase coefficient. After satisfying the initial phase condition, the beams emitted by the optical antenna array will interfere with each other to form a quasi-Bessel beam.

[0021] Furthermore, under the initial phase conditions, an additional deflection voltage is applied to the phase modulation array. This deflection voltage gives the phase of the emitted light from the optical antenna array a linearly distributed deflection phase in both directions, which can achieve arbitrary angle deflection of the beam.

[0022] Furthermore, the sensing electrode is exposed on the uppermost layer of the probe arm and connected to the probe base via a lower metal wire covered with a silicon dioxide layer. The sensing electrodes are located at the edge of the probe arm and their function is to sense the potential changes in the stimulated area.

[0023] This invention achieves a two-dimensional distributed optical antenna array by uniformly arranging microwaveguide grating antennas in two orthogonal directions. This optical antenna array, together with an optical beam splitter modulation array, constitutes a two-dimensional optical phased array. Compared with traditional one-dimensional optical phased arrays, the two-dimensional optical phased array in this invention enables two-dimensional scanning of a single-wavelength laser. That is, it does not require changing the wavelength of the emitted light; arbitrary angle deflection of the beam can be achieved simply by controlling the phase of the emitted light from each microwaveguide grating antenna. This characteristic is more suitable for applications sensitive to laser wavelength. Furthermore, the two-dimensional optical phased array allows for flexible wavefront control and beam shaping in two orthogonal directions, making it easier to achieve high-quality quasi-Bessel beams.

[0024] This invention also provides a working process for an all-solid-state optical biological probe based on the principle of optical phased array, the steps of which are as follows:

[0025] First, the probe's optical and electrical interfaces are connected to an external laser source, power supply, drive module, and signal processing module. Then, the probe arm is implanted into the biological tissue, while the probe base remains outside. The external laser source is coupled into the optical path system on the probe chip via an input optical coupler, and then enters a 1×n optical switch. The 1×n optical switch is controlled to pass the laser through one or more optical beam modulation arrays. The control voltage of the phase modulation array is adjusted to ensure the laser meets initial amplitude and phase conditions. The laser is then emitted from the optical antenna array into external space, forming a quasi-Bessel beam. By further controlling the voltage of the phase modulation array, the beam's pointing position is changed, thus achieving optical stimulation of biological tissues in various locations. Finally, optogenetic studies are conducted by reading changes in the electrical signals of the sensing electrodes, analyzing relevant biochemical indicators, and observing the biological physiological state and behavior.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] (1) Based on the principle of optical phased array, this invention can achieve all-solid beam pointing. The beam pointing switching speed is fast, which is determined by the phase modulation response time of the phase shifter array, usually in the order of microseconds or even nanoseconds. The beam can be continuously scanned and has high spatial resolution.

[0028] (2) The present invention utilizes optical switches to select optical antenna arrays located at different positions, which can achieve single-point or multi-point optical stimulation of biological tissues over a larger area.

[0029] (3) Conventional one-dimensional optical phased arrays require significant changes in the wavelength of light to achieve beam scanning in one direction, and large-scale changes in the wavelength of light can cause significant differences in the response sensitivity of stimulated proteins and tissues. This invention utilizes a two-dimensional distributed optical antenna array, which can achieve beam deflection of a single wavelength laser by controlling the phase distribution in two dimensions, making it more suitable for applications of optical probes.

[0030] (4) By setting the amplitude and phase distribution of the emitted light of the optical phased array, the present invention synthesizes a quasi-Bessel beam. This type of beam has a non-diffraction propagation range. Within this range, the quasi-Bessel beam has small propagation diffraction and can still recover to the original transverse light intensity distribution after encountering a small obstacle. It has a stronger penetrating ability in biological tissues. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the optical beam splitting modulation structure of the present invention;

[0033] Figure 3 This is a schematic diagram of the optical antenna array structure of the present invention.

[0034] Figure 4 This is a schematic diagram of the cross-sectional structure of the device of the present invention.

[0035] Among them, 1 is the probe base, 2 is the probe arm, 3 is the input optical coupler, 4 is the 1×4 optical switch, 5 is the optical beam splitter modulation array, 6 is the electrical interface, 7 is the sensing electrode, 8 is the optical antenna array, 9 is the optical beam splitter network, 10 is the amplitude modulation array, 11 is the phase modulation array, 12 is the 1×2 multimode interference coupler, 13 is the directional coupler, 14 is the thermo-optical phase shifter, 15 is the micro waveguide grating antenna, 16 is the silicon substrate, 17 is the buried oxide layer, 18 is the silicon waveguide device layer, 19 is the silicon dioxide layer, 20 is the silicon nitride waveguide device layer, 21 is the titanium nitride metal layer, 22 is the copper metal layer, 23 is the metal via, and 24 is the exposed metal layer. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments described below are merely some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] The overall structure of the present invention is shown below. Figure 1As shown, the all-solid-state optical biological probe based on the principle of optical phased array comprises two parts: a probe base 1 and a probe arm 2. Both parts are fabricated on the same silicon-based optical chip, forming an all-solid-state structure. The probe base includes an input optical coupler 3, a 1×4 optical switch 4, four optical beam splitter modulation arrays 5, and multiple electrical interfaces 6. The input optical coupler 3 serves as the probe's optical interface, connecting to an external optical fiber or laser. The optical output end of the input optical coupler 3 is connected to the optical input end of the 1×4 optical switch 4 via a single-mode waveguide. The four optical output ends of the 1×4 optical switch 4 are connected to the optical input ends of the four optical beam splitter modulation arrays 5 via single-mode waveguides, respectively. The four optical beam splitter modulation arrays 5 have identical structures. The electrical interfaces 6 are used to connect to external electrical modules. The probe arm 2 includes multiple sensing electrodes 7 and four optical antenna arrays 8. The sensing electrodes 7 are connected to some of the electrical interfaces 6 in the probe base 1 via copper wires covered with silicon dioxide. The four optical antenna arrays 8 are completely identical in structure except for their positions on the probe arm; the optical input end of the optical antenna array 8 is connected to the optical output end of the optical beam splitter and modulator array 5 in the probe base 1 through 64 single-mode waveguides.

[0038] The structure of the optical beam splitter modulation array 5 is as follows: Figure 2 As shown, the array includes an optical beam splitter network 9, an amplitude modulation array 10, and a phase modulation array 11. The optical beam splitter network 9 consists of 63 1×2 multimode interference couplers 12 cascaded in a six-level tree structure. The optical output of the optical beam splitter network 9 is connected to the optical input of the amplitude modulation array 10 via 64 single-mode waves. The amplitude modulation array 10 consists of 64 directional couplers 13 arranged in parallel, and its optical output is connected to the optical input of the phase modulation array 11 via 64 single-mode waves. The phase modulation array 11 consists of 64 thermo-optical phase shifters 14. Each thermo-optical phase shifter 14 includes a single-mode waveguide and a titanium nitride heating resistor. This electrode is connected to a portion of the electrical interface 6 in the probe base via a copper wire covered with silicon dioxide.

[0039] The structure of optical antenna array 8 is as follows Figure 3 As shown, it consists of 64 microwaveguide grating antennas 15 arranged in an 8x8 two-dimensional distribution in two orthogonal directions. On-chip laser is input into each microwaveguide grating antenna 15 through 64 single-mode waveguides, and the microwaveguide grating antennas 15 radiate the on-chip laser into the off-chip space, where they interfere with each other to form a specific beam.

[0040] The working principle of this invention is as follows:

[0041] This invention utilizes an input optical coupler 3 to couple external laser light into a single-mode optical waveguide within the chip. The light is then transmitted to a 1×4 optical switch 4, which is a single-ended optical input and four-ended optical output structure, formed by a tree-like cascade of three 1×2 Mach-Zehnder interferometer-type thermo-optical switches. The input of this Mach-Zehnder interferometer-type thermo-optical switch is a 1×2 multimode interference coupler, and the output is a 2×2 multimode interference coupler, connected by two single-mode optical waveguides. A titanium nitride thermistor is located 2µm above one of the single-mode optical waveguides. By applying a voltage across the thermistor, the optical power at the two output ports is controlled. Applying a voltage to the 1×4 optical switch 4 controls the input laser source to output from one or more of the output ports.

[0042] The optical beam splitter network 9 is composed of 63 1×2 multimode interference couplers 12 cascaded in a six-level tree structure, which can evenly split the input light of a single-mode optical waveguide into 64 single-mode optical waveguides and output it to the amplitude modulation array 10.

[0043] The amplitude modulation array 10 consists of 64 directional couplers 13 arranged in parallel. The amplitude of the output light of each directional coupler 14 is related to the amplitude of the input light and the coupling length. Each directional coupler 14 has a specific coupling length, modulating multiple input lights with equal amplitude distribution into multiple output lights with a specific amplitude distribution. The specific amplitude distribution satisfies an initial amplitude condition, which ensures that the amplitude A of the radiated light finally transmitted to the microwaveguide grating antenna in the nth row and mth column of the antenna array is... nm for:

[0044]

[0045] In the formula, N is the number of rows and columns of the optical antenna array, representing the array size. In this example, N = 8; S is a positive coefficient less than or equal to 1. In this example, S = 0.5.

[0046] The phase modulation array 11 consists of 64 thermo-optical phase shifters 14, each containing a single-mode waveguide and a titanium nitride heating resistor located 2 μm above the single-mode waveguide. By independently applying a voltage to each titanium nitride heating resistor, the phase distribution output from each single-mode optical waveguide to the optical antenna array 8 is changed; this phase distribution must first satisfy an initial phase condition. This initial phase condition ensures that the phase Φ of the light radiated by the microwaveguide grating antenna 15 in the nth row and mth column of the optical antenna array... n for:

[0047]

[0048] In the formula, N is the number of rows and columns of the optical antenna array, representing the array size. In this example, N = 8. In the formula, Φ0 is a positive phase coefficient. In this example, Φ0 = 2π.

[0049] The optical antenna array 8 consists of multiple microwaveguide grating antennas 15 arranged in an 8x8 two-dimensional array in two orthogonal directions. Each microwaveguide grating antenna 15 is a grating formed by full waveguide etching, occupying an area of ​​less than 2μm × 4μm, and can radiate laser light from inside the waveguide into the surrounding space over a short distance. After satisfying the initial amplitude and initial phase conditions, the light emitted by each microwaveguide grating antenna 15 will interfere with each other to form a quasi-Bessel beam.

[0050] Under the initial phase conditions, an additional deflection voltage is applied to the phase modulation array 11. This deflection voltage introduces an additional deflection phase that is linearly distributed in both row and column directions into the emitted light of the optical antenna array 8, enabling arbitrary angle deflection of the quasi-Bessel beam. The deflection angle is related to the slope of the linear distribution of the deflection phase in the corresponding direction.

[0051] The sensing electrode 7 is exposed on the uppermost layer of the probe arm 2 and is located near the optical antenna array 8. When the potential of the stimulated area changes, the change is transmitted through a copper metal wire covered with a silicon dioxide layer 19 connected to the sensing electrode 7 to the electrical interface 6 of the probe base 1, and then to the external electrical module.

[0052] The cross-sectional structure of the device of the present invention is as follows Figure 4 As shown, the device includes a silicon substrate 16, a buried oxide layer 17, a silicon waveguide device layer 18, a silicon dioxide layer 19, a silicon nitride waveguide device layer 20, a titanium nitride metal layer 21, a copper metal layer 22, a metal via 23, and an exposed metal layer 24. The fabrication process of the device is as follows: all on-chip optical components are etched into the silicon waveguide device layer 18 and the silicon nitride waveguide device layer 20; the titanium nitride metal layer 21 is used to fabricate a titanium nitride heater; the copper metal layer 22 and the metal via 23 are used for electrical interconnection; the exposed metal layer 24 is used to fabricate sensing electrodes and electrical interfaces; the silicon substrate 16 of the probe base 1 is retained; and the silicon substrate of the probe arm 2 needs to be completely removed by back-etching.

Claims

1. A fully solid-state optical biological probe based on the principle of optical phased array, characterized in that, The device comprises two parts: a probe base (1) and a probe arm (2), both of which are fabricated on the same silicon photonic chip in a solid-state structure. The probe base (1) includes, in sequence, an input optical coupler (3), a 1×n optical switch (4), and n optical beam splitter modulation arrays (5) according to the optical path. The optical beam splitter modulation arrays (5) include, in sequence, an optical beam splitter network (9), an amplitude modulation array (10), and a phase modulation array (11) according to the optical path. Each optical structure on the probe base (1) passes through a single optical path in sequence. One or more single-mode waveguides are connected in sequence; the probe base (1) also includes multiple electrical interfaces (6) for connecting to external electrical modules; the probe arm (2) includes multiple sensing electrodes (7) and n optical antenna arrays (8); the sensing electrodes (7) and some of the electrical interfaces (6) in the probe base (1) are connected by copper metal wires covered with silicon dioxide; the optical input end of the optical antenna array (8) is connected to the optical output end of the optical beam splitter modulation array (5) in the probe base (1) through multiple single-mode waveguides. The optical antenna array (8) consists of multiple micro waveguide grating antennas (15) arranged in two orthogonal directions in a two-dimensional antenna array of N rows and N columns. On-chip lasers are radiated out into the off-chip space through the optical antenna array (8). The amplitude modulation array (10) consists of multiple directional couplers (13) arranged in parallel. By setting the coupling length of each directional coupler, the multiple input lights with equal amplitude distribution are modulated into multiple output lights that meet the initial amplitude condition. The initial amplitude condition is the amplitude A of the light radiated by the micro waveguide grating antenna (15) in the nth row and mth column of the optical antenna array (8). nm satisfy: In the formula, N is the number of rows and columns of the optical antenna array; S is a positive coefficient less than or equal to 1; Under the condition of satisfying the initial amplitude, by applying an initialization voltage to the phase modulation array (11), the emitted light of the optical antenna array (8) satisfies the initial phase condition, which is such that the phase Φ of the emitted light from the micro waveguide grating antenna (15) in the nth row and mth column of the optical antenna array (8) is... n for: In the formula, N is the number of rows and columns of the optical antenna array, and Φ0 is a positive phase coefficient. After the initial phase condition is met, the light emitted by the optical antenna array (8) will interfere with each other to form a quasi-Bessel beam.

2. The all-solid-state optical biological probe based on the principle of optical phased array according to claim 1, characterized in that: The 1×n optical switch (4) is a thermally modulated optical switch or an electrically modulated optical switch with single-ended optical input and n-ended optical output; Applying a voltage to the 1×n optical switch (4) can control the input laser source to output from one or more of its output ports.

3. The all-solid-state optical biological probe based on the principle of optical phased array according to claim 1, characterized in that: The optical beam splitting network (9) is composed of multiple 1×2 multimode interference couplers (12) cascaded together, which is used to split one beam into multiple beams of equal power and output them to the amplitude modulation array (10) through multiple single-mode waveguides.

4. The all-solid-state optical biological probe based on the principle of optical phased array according to claim 1, characterized in that: The phase modulation array (11) consists of multiple thermally or electrically modulated phase shifters (14), which independently control the phase of each output light by an applied voltage.

5. The all-solid-state optical biological probe based on the principle of optical phased array according to claim 1, characterized in that: After forming a quasi-Bessel beam, an additional deflection voltage is applied to the phase modulation array (11). This deflection voltage introduces a deflection phase that is linearly distributed in both directions into the emitted light of the optical antenna array (8), which can achieve arbitrary angle deflection of the beam.

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