A cavity-in laser energy transmission positioning integrated system based on a coupled cavity laser

Abstract

The application relates to a cavity-in-laser energy transmission positioning integrated system based on a coupled cavity laser, which comprises a transmitter and a receiver integrated into a remote user equipment, a main resonant cavity composed of elements in the transmitter and the receiver and a free space resonant cavity which is mutually coupled with the main resonant cavity; the main resonant cavity is located in the transmitter and is used for generating cavity-in-laser and is composed of a first return reflector, a gain medium and a second return reflector which are arranged in sequence along an optical path, and the gain medium is connected with a pump source; the free space resonant cavity is composed of a third return reflector integrated in the transmitter and a fourth return reflector integrated in the receiver and used for providing effective optical frequency electromagnetic field feedback, and the third return reflector is mutually beam-coupled with the second return reflector; the application realizes the perception of 3D position through the double-cavity coupling principle and the design of the multiple reflectors and based on the inherent self-alignment function, improves the energy transmission efficiency and the field of view FoV, and realizes the mobile positioning.

Description

Technical Field

[0001] This invention relates to the field of positioning and energy transfer technology, and in particular to an integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser. Background Technology

[0002] In dynamic Internet of Things (IoT) scenarios, the intelligent sensing and collaboration of unmanned devices such as drones (UAVs), industrial robots, and modular spacecraft have garnered significant attention, raising two key questions: i) how to ensure the energy consumption required for a single node to maintain its computing and communication capabilities; and ii) how to achieve high-precision and highly adaptable autonomous collaboration among heterogeneous nodes. Therefore, in the IoT era, the demand for sufficient and convenient power supply and high-precision positioning is becoming increasingly prominent. To address this, new methods and systems based on wireless power transfer (WPT), communication, sensing, and positioning using acoustic, electrical, and optical (visible light or laser) technologies have been extensively developed. However, existing technologies still face challenges in providing high-power energy for mobility and easily integrated sensing capabilities.

[0003] To achieve simultaneous transmission of energy and location information, existing simultaneous energy and information transmission technologies (SWIPT) based on evanescent beams or non-directional radiation cannot simultaneously meet the three transmission characteristics of "long distance, high power, and high security." Systems based on directional radiation have the potential to satisfy these three requirements simultaneously. Typical solutions include beamforming for communication and energy focusing for energy transmission. Among these, WPT based on split-cavity lasers (DSCLs), also known as resonant beam charging (RBC), uses intracavity lasers as the carrier of high-power energy and high-speed data transmission and has been proposed and studied. RBC is also considered one of the driving factors for 6G networks.

[0004] In recent years, the design and optimization of systems for energy and information transmission via intracavity lasers (ICLs) have received increasing attention. These studies have analyzed key system performance parameters, including output power, transmitter field of view, foreign object surface radiation exposure, signal-to-noise ratio, and communication rate. However, existing DSCL-based systems still suffer from bottlenecks such as limited field of view, low end-to-end energy efficiency, and immature signal modulation schemes. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide an integrated intracavity laser energy transfer and positioning system based on a coupled cavity laser.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] An integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser includes a transmitter and a receiver integrated into a remote user equipment, and a main resonant cavity composed of components in the transmitter and receiver, and a free-space resonant cavity coupled to the main resonant cavity.

[0008] The main resonant cavity is located in the transmitter and is used to generate intracavity laser. It consists of a first retroreflector, a gain medium, and a second retroreflector arranged sequentially along the optical path. The gain medium is connected to the pump source.

[0009] The free-space resonant cavity consists of a third retroreflector integrated in the transmitter and a fourth retroreflector integrated in the receiver for providing effective optical frequency electromagnetic field feedback. The third retroreflector and the second retroreflector are beam-coupled to each other.

[0010] The transmitter also includes: a beam-capturing unit for estimating the angle of arrival (AoA), a ranging unit, and a microcontroller unit that receives the AoA estimation and ranging results and obtains the positioning information.

[0011] Furthermore, the beam capturing unit includes a CMOS image sensor disposed at the end of the first retroreflector away from the second retroreflector for capturing the beam; the CMOS image sensor is connected to a microcontroller unit.

[0012] Furthermore, the AoA estimation step includes:

[0013] The light field distribution on the CMOS image sensor is obtained, the position of the light spot on the CMOS image sensor is obtained according to the centroid algorithm, and the position of the target is determined by the position of the light spot on the CMOS image sensor; the estimation error of the angle of arrival (AoA) is obtained according to the beam intensity distribution, CMOS responsivity and noise; and then the estimated angle of arrival (AoA) is obtained.

[0014] Furthermore, the CMOS image sensor obtains photoelectrons on each pixel. This includes the electrical power converted from the incident laser beam and the noise power on the CMOS sensor:

[0015]

[0016] in, and These are photoelectrons caused by the loading signal and noise on the intracavity laser, respectively. It refers to the CMOS responsivity. It is quantum efficiency; and It represents the maximum intensity and normalized field distribution occurring on CMOS.

[0017] The estimation error of AoA is obtained based on beam intensity distribution, CMOS responsivity, and noise.

[0018] Wherein, the variance of the estimation error along the Y-axis The expression is as follows:

[0019]

[0020] in, This refers to the noise variance in CMOS. It is the index value of the CMOS pixel.

[0021] Furthermore, the noise variance in the CMOS includes impulse noise caused by the incident laser beam. Reading noise Pixel inherent noise Dark current noise and background light noise , pixels The noise variance is expressed as:

[0022]

[0023] in, It is photoelectrons caused by noise on the intracavity laser; It is the CMOS responsivity; and It represents the maximum intensity and normalized field distribution occurring on CMOS.

[0024] Furthermore, the ranging unit performs ranging based on the self-mixing characteristics and inherent polarization modulation of DCCL. A polarization rotator is placed between the third and fourth retroreflectors to induce polarization mode switching, and the switching frequency in the reflected beam is found. To estimate the distance to the target.

[0025] Furthermore, a beam-splitting mirror M is placed between the polarization rotator and the third retroreflector, and a portion of the reverse beam is sent to a spectrum analyzer to find the polarization self-modulation spectrum; the length of the spatial resonant cavity... Depend on Determine d by determining the frequency switching period t:

[0026]

[0027] In the formula, It is the speed of light.

[0028] Furthermore, the portion of the reverse beam separated by the beam-splitting mirror M is collected by the Wollaston prism and separated into two polarization components; the intensity of one component is detected by a photodiode and sent to a spectrum analyzer to find the polarization self-modulation spectrum; the other component is collected by another photodiode and sent to a frequency counter controlled by a computer PC.

[0029] Furthermore, the receiver integrates a photovoltaic cell for converting intracavity laser light into electrical energy.

[0030] Furthermore, the coupled cavity laser operates the main resonant cavity under a high threshold condition by setting the reflectivity of the second and third retroreflectors, thereby preventing the main resonant cavity from independently generating laser light after being pumped by a pump source.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention proposes an integrated energy transfer and positioning system based on a split-cavity laser (DCCL), building upon the DSCL-based SWIPT, to improve energy transfer efficiency and field of view (FoV) and achieve mobile positioning. Due to the dual-cavity coupling principle and the multi-reflector (RR) design, energy transfer efficiency is directly improved, and 3D position sensing is achieved through inherent self-alignment functionality.

[0033] The free-space cavity coupled in this invention acts as an effective reflector, with its reflectivity closer to the optimal value. Therefore, at a given pump power, using a DCCL can achieve higher output power than using a DSCL.

[0034] Furthermore, the DCCL design of this invention places the gain medium within the main resonant cavity. Since the main resonant cavity in a DCCL does not require a large FoV, there is no need to sacrifice gain amplification. The transmitter FoV is improved by increasing the FoV of the retroreflector CRR3 located on the transmitter side of the free-space resonant cavity. This overcomes the difficulty in compromising between the transmitter field of view and system gain in a DSCL, thus allowing for a larger field of view in a DCCL.

[0035] Because the main resonant cavity and the free space resonant cavity are tightly coupled together through the specific design of this invention, foreign objects intruding into the free space resonant cavity will disrupt the generation conditions of DCCL, giving the system an inherent safety characteristic.

[0036] The high-power intracavity laser beam on the receiver of this invention is converted into electrical energy by a photovoltaic cell for wireless charging. Since the transmitter can wirelessly transfer power to the receiver, the DCCL power transfer and positioning integrated system allows for cold start-up of IoT devices with integrated receivers. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the integrated power transfer and positioning system based on DCCL according to the present invention;

[0038] Figure 2 A comparative diagram of the performance of a DCCL system to compare the working principle of DSCL; (a) Working principle of a split-cavity laser system; (b) Power transfer enhancement mechanism of a split-cavity laser system; (c) Field angle enhancement mechanism of a split-cavity laser system.

[0039] Figure 3 A schematic diagram of the DCCL system positioning analysis; (a) coordinate system and structural model for DCCL system simulation analysis; (b) equivalent reflective area of ​​the CRR surface;

[0040] Figure 4 A schematic diagram illustrating the ranging frame;

[0041] Figure 5 A schematic diagram illustrating the AoA estimation framework: (a) Spot capture using CMOS. (b) Centroid calculation of the spot on CMOS;

[0042] Figure 6 This is a schematic diagram of the equivalent circuit of a PV.

[0043] Figure 7 Schematic diagram of the performance improvement brought about by the design of DCCL; (a) Output laser power corresponding to different reflectivities R2; (b) Output power corresponding to different reflectivities R4;

[0044] Figure 8 The output laser power P of DSCL and DCCL systems out With pump power P in A schematic diagram showing the relationship between the Z-axis transmission distance d and the Z-axis transmission distance d.

[0045] Figure 9 P under different CRR3 designs for DSCL and DCCL systems out A schematic diagram showing the relationship between the transmitter FoV and the transmitter.

[0046] Figure 10 A schematic diagram of the AoA estimation accuracy of the DCCL-energy-transfer and positioning integrated system;

[0047] Figure 11 This is a schematic diagram of the WPT wireless power transmission performance of the DCCL-Power Transmission and Positioning Integrated System. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0049] Example 1

[0050] Existing research indicates that: i) DSCL-based systems face performance limitations, such as finite FoV; ii) the sensing and localization problem of DCCL-based systems warrants further exploration. Therefore, this invention proposes a DCCL-based integrated energy transfer and localization system. This system, based on the coupling of two resonant cavities, can significantly improve the energy transfer efficiency and FoV of DSCL-based systems. Furthermore, this invention proposes angle estimation based on beam trapping and distance estimation based on feedback modulation, utilizing the inherent self-alignment and self-mixing effects of the intracavity laser in the DCCL to achieve integrated energy transfer and localization.

[0051] I. System Structure

[0052] like Figure 1 The structure of the proposed DCCL (Distributed DC-Channel Laser) power transfer and positioning integrated system is shown. This system design utilizes a cat's-eye retroreflector (CRR). Similar to DSCL-based systems, the DCCL power transfer and positioning integrated system includes a transmitter and a receiver integrated into a remote user equipment. CRR1, the gain medium, and CRR2 constitute the main resonant cavity, the primary subsystem for generating intracavity laser. CRR3 and CRR4 integrated into the receiver form the free-space resonant cavity subsystem. If the gain medium receives sufficient pump power, intracavity laser can automatically form as long as the receiver is within the transmitter's FoV range, thus establishing a mobile energy and information transmission channel. Therefore, due to the integration of CRRs, the self-alignment function of the DSCL system is still guaranteed in the DCCL system. CRR2 and CRR3 require specially designed reflectivities to ensure that the intracavity laser cannot be excited in the main resonant cavity without beam feedback from the free-space resonant cavity. Therefore, under this working mechanism, if a foreign object intrudes into the free-space cavity, the intracavity laser generation conditions will be automatically disrupted, and the intracavity laser will immediately stop being excited, thus ensuring human safety.

[0053] The self-alignment function offers the advantage of using intracavity laser for angle of arrival (AoA) estimation, as the position of the beam spot that can be captured on the CRR1 precisely reflects the receiver's position in three-dimensional space. In the transmitter, complementary metal-oxide-semiconductor (CMOS) is used for beam capture, and then a centroid algorithm is executed to obtain the beam center. Furthermore, a beam splitter and a time-of-flight (ToF) module are integrated into the transmitter, utilizing the self-mixing properties of DCCL and its inherent polarization modulation for ranging. A microcontroller unit (MCU) is integrated into the transmitter to collect the receiver's positioning information. Finally, a photovoltaic panel is integrated into the receiver to convert the intracavity laser into electrical energy, providing power to watt-level IoT devices. This invention also provides AoA estimation, ranging, and power conversion schemes based on the above system.

[0054] II. Coupled Cavity Principle

[0055] The present invention relates to the energy transfer and FoV enhancement principles of the DCCL system.

[0056] 1) Principle Overview: To explain the principle of a distributed coupled-cavity laser (DCCL), we will first introduce the principle of a distributed single-cavity laser (DSCL) system. For example... Figure 2 As shown in (a), the generation of DSCL requires the following three key elements: 1) a pump source (excitation system) to enable and maintain population inversion in the activating material, providing the energy source for the system; 2) an activating material to achieve population inversion and stimulated emission amplification, supporting the amplification or maintenance of optical-frequency electromagnetic fields with multiple oscillation modes within the cavity; and 3) a main resonant cavity coupled to a free-space open optical resonant cavity, providing optical feedback capability to the activating material and ensuring the continuous oscillation of stimulated emission photons generated by the activating material. These principles bring about the inherent characteristics of the DSCL system, namely, high transmittable power and self-alignment, safety for human skin, and the potential for ultra-long-range transmission.

[0057] like Figure 2 (a) The DCCL system proposed in this invention includes at least two mutually coupled resonant cavities, namely a main cavity and a coupled free-space cavity, and four retroreflectors (here, the cat's eye retroreflector, CRR, mentioned below, is taken as an example). It is worth noting that the effective operation of DCCL requires the following conditions to be met: 1) The main resonant cavity and the free-space resonant cavity based on the retroreflection structure provide optical feedback capability in the moving state of the system receiver; 2) Various system components such as the activating material and telescope structure located in the pupil of the main resonant cavity or the free-space resonant cavity provide the necessary characteristics to maintain the laser oscillation in the cavity; 3) The high-threshold main resonant cavity, which cannot operate independently, can only generate intracavity laser when CRR1, CRR2, and CRR3 are aligned with CRR4, which can provide effective optical frequency electromagnetic field feedback.

[0058] As proposed in existing coupled-cavity laser designs, the coupled free-space cavity acts as an effective reflector, with its reflectivity closer to the optimal value. Therefore, at a given pump power, a DCCL can achieve higher output power than a DSCL. Furthermore, the DCCL design overcomes the "difficulty in compromising between emitter field of view and system gain" in DSCL, allowing for a larger field of view. Because the main resonator and free-space resonator are tightly coupled through the specific design of this invention, foreign objects intruding into the free-space resonator will disrupt the DCCL generation conditions, giving the system the same inherent safety characteristics as DSCL. Specifically, to improve the safety of the DCCL, this invention allows for specific design of the CRR reflectivity, enabling the main resonator to operate under high threshold conditions, thus preventing the main resonator from independently generating laser light after being pumped by a pump source. Based on this design, the DCCL achieves increased energy transfer efficiency and FoV enhancement, which will be described in detail below.

[0059] 2) Improved energy transfer efficiency: In a DCCL, one of the retroreflectors in the main resonant cavity, i.e. Figure 2 (b) The reflectivity of CRR2 is quite low (e.g., 60% or less) to ensure that the laser in the main resonant cavity does not oscillate. Simultaneously, the free-space resonant cavity is equivalent to a Fabry-Perrot (FP) cavity (or etalon). Interference occurs between the laser in the main resonant cavity and the laser in the free-space resonant cavity on the mirror of CRR2 / 3 because the two beams, satisfying the coherence condition and propagating in opposite directions, meet at CRR2 / 3. This causes the maximum and minimum values ​​of the lasers propagating in the two cavities to alternate periodically with wavelength. In DCCL, a portion of the beam enters the main resonant cavity from the free-space resonant cavity and generates external cavity laser feedback on the gain medium within the main resonant cavity. This external cavity feedback leads to the interference condition on the mirror of CRR2 / 3, which is equivalent to increasing the mirror reflectivity at the output end of the main resonant cavity for the interference enhancement band, reducing losses, and enabling the main resonant cavity to meet the laser excitation requirements at this point.

[0060] like Figure 2 In case (b), in the interference enhancement band, the effective reflectivity of the free-space resonant cavity relative to the laser within the main resonant cavity is expressed as:

[0061]

[0062] in, and These are the reflectances of CRR2 / 3 and CRR4, respectively. It is the phase difference caused by the optical path length in the free-space resonant cavity.

[0063] If the main resonant cavity has no external free-space resonant cavity feedback, its threshold pump power should be:

[0064]

[0065] in, It is the intracavity laser transmission efficiency of the main resonant cavity. , , These represent the laser transmission efficiency inside the gain medium, the cross-sectional area of ​​the gain medium, and the saturation intensity of the gain medium, respectively. This is the extraction efficiency (represented by the ratio of output laser power to the total usable power of the upper energy level). Under beam feedback in a free-space resonant cavity, R2 will be filtered by R, which has a higher reflectivity. eff Replacement. Therefore, for DCCL, the presence of a free-space resonator will reduce the pump threshold of the main resonator ( , , , The values ​​are all in the range of 0 to 1, which can guarantee that the same Increase the output power of the DCCL system under the given conditions.

[0066] 3) FoV Enhancement: Both the FoV of the transmitter and the FoV of the receiver limit the overall FoV of the system. In practice, in split-cavity laser systems, improving the FoV of the receiver is relatively easy through optical element design, such as using retroreflector arrays. However, improving the FoV of the transmitter has always been a challenge. In a split-cavity laser system, the gain medium on the transmitter side can amplify two types of incident beams: i) the intracavity laser beam oscillating back and forth within the cavity; ii) arbitrary free photons generated by spontaneous emission from the gain medium or scattered from the intracavity laser or other sources. If arbitrary free photons are excessively amplified by the gain medium, the resulting light intensity will be similar to the saturation intensity of the gain medium, thus significantly reducing the effective gain used to excite the intracavity laser. However, for DSCL systems, a larger field of view of the gain medium increases the likelihood of arbitrary free photon amplification. Therefore, there is an inherent compromise between the field of view of the gain medium and the maximum gain it can produce. The constraint relationship between the small-signal gain and FoV of the gain medium in a laser resonator is given by the following formula.

[0067]

[0068] in, It is a small-signal gain factor. It is the solid angle on the gain dielectric side. It is the cross-sectional area of ​​the gain medium. It is the length of the gain medium. It is the refractive index of the gain medium. It is the spacing between the gain medium and the near-end retroreflector.

[0069] Therefore, in Figure 2 (c) In the DSCL shown in the left figure, the FoV of the transmitter is limited by the solid angle of the gain medium, which cannot be improved even with a specific retroreflector design using a larger FoV at the transmitter. However, in the DCCL, as... Figure 2 (c) In the right figure, the gain medium is placed inside the main resonant cavity. In a DCCL, the main resonant cavity does not require a large FoV, therefore no sacrifice in gain is necessary. For a DCCL, we can improve the emitter FoV by increasing the FoV of the retroreflector CRR3 located on the emitter side in the free-space resonant cavity. In this case, CRR1 and CRR2 have smaller FoVs, while CRR3 has a larger FoV. Intracavity lasers (in the free-space resonant cavity) from a larger field of view can be collected by CRR3 and then coupled to CRR2. Beam coupling between CRR2 and CRR3 can be achieved through specific coupling element design or by directly reducing the focal length of the lens in CRR3. Assume the focal length of the lens in CRR2 is... The focal length of the lens in CRR3 is (like Figure 3 (As shown), the incident angles on CRR2 and CRR3 at this time and for

[0070]

[0071]

[0072] in, It is the distance the light spot deviates from the center of the mirror in CRR2 / 3. Therefore, .when < At the same time, the maximum permissible incident beam angle of CRR3 (usually considered to be half of FoV) is larger than that of CRR2. In addition, intracavity lasers can pass directly through the mirrors of CRR2 / 3 without the need for specific beam guiding elements.

[0073] III. Integrated Energy Transfer and Positioning Method

[0074] In the invented DCCL power transfer and positioning integrated system, three-dimensional positioning is achieved through joint angle estimation (i.e., two-dimensional coordinates in space) and range estimation. Furthermore, a high-power intracavity laser beam on the receiver is converted into electrical energy via a photovoltaic cell for wireless charging. Since the transmitter can wirelessly transfer power to the receiver, the DCCL power transfer and positioning integrated system allows for cold start-up of IoT devices with integrated receivers. This section will introduce the angle and range estimation schemes and accuracy analysis. Following this, a photovoltaic equivalent circuit model for charging power analysis will be presented.

[0075] A. Distance estimation

[0076] 1) Ranging Scheme: In DCCL, a ranging scheme based on polarization self-modulation (PSM) is adopted, utilizing the light-induced feedback effect, i.e., self-mixing interferometry. Assuming the output beam of the main resonant cavity consists of two orthogonal linear polarization modes, the beam propagates back to the main resonant cavity after one round trip in the free-space resonant cavity. A polarization rotator then induces a switching of the polarization modes. In other words, the polarization direction of the reflected beam automatically and periodically switches between the two modes. The switching frequency... It can be used To identify, This represents the length of the free-space resonant cavity. Therefore, if the CRR4 is embedded in a target, the distance to the target can be determined by finding the distance in the reflected beam. To estimate.

[0077] like Figure 4 The diagram illustrates the ranging framework, where BS is the beam splitter, FBC is the feedback controller, and PD is the photodetector. The intracavity laser from the main resonant cavity maintains two linear polarization modes. and After passing through a quarter-wave plate (QWP), the fast (or slow) axis of the polarization direction of the laser in the output cavity is rotated by 45°. The laser beam then propagates in free space and is reflected by a CRR4. Next, the laser beam passes through the QWP again, rotating its polarization direction by 90° relative to the original polarization direction of the beam from the main cavity. Using a beam-splitting mirror M, a portion of the reversed beam is collected by a Wollaston prism (WP), where the two polarization components are separated. The intensity of one component is detected by a photodiode (PD) and sent to a spectrum analyzer to find the PSM spectrum. The other component is collected by another PD and sent to a computer-controlled frequency counter to measure the number of cycles per second of oscillations or pulses in the periodic electronic signal. The two spectra are displayed as waveforms 180° out of phase with each other.

[0078] like Figure 4 As shown, can be Confirmed. At the same time, It is a cycle with twice the round-trip time, that is Therefore, the frequency switching period can be determined. t To estimate d ,Right now

[0079]

[0080] 2) Accuracy Analysis: The ranging accuracy of the above scheme is determined by the search... The accuracy is determined by the amplitude of f, and the range resolution is determined by the amplitude of f fluctuation. For spectral analysis, the time scale is 10. div The ranging accuracy can reach the millimeter level, and the target distance is at the meter level.

[0081] B. AoA estimation

[0082] 1) Beam point position acquisition: Due to the inherent self-alignment characteristics of the DCCL system, the position of the laser spot within the transmitter's cavity, i.e., its two-dimensional coordinates, corresponds to the two-dimensional coordinates of the receiver. For example... Figure 5 As shown in (a), assume that a small portion of the intracavity laser outputs from M1 and strikes the CMOS. Figure 5 (b) The position of the light spot on the CMOS shown can be estimated using the traditional center point algorithm.

[0083]

[0084] in, It is the photoelectrons on each pixel. This is the index value of the CMOS pixel. The optimized centroid algorithm can be used in various application scenarios. According to... Figure 3 Estimate the two-dimensional coordinates of the target and The relationship between them is described as

[0085]

[0086] in, This refers to the estimated range. It can be seen that the estimated two-dimensional coordinates of the target are equivalent to the beam point position on the CMOS. The estimation. Therefore, this invention uses analysis The estimation accuracy is used to explain the positioning accuracy in detail.

[0087] 2) Accuracy Analysis: Several factors contribute to the error in 2D coordinate estimation, such as laser intensity noise and CMOS-induced noise. Laser intensity noise mainly originates from spontaneous emission, which affects the output laser of M1. Furthermore, noise is also induced during photoelectric conversion and analog-to-digital conversion in the CMOS. Therefore, in (6)... This includes the electrical power converted from the incident laser beam and the noise power on the CMOS, i.e.

[0088]

[0089] in, and These are photoelectrons caused by the loading signal and noise on the intracavity laser, respectively. It refers to the CMOS responsivity. It is the quantum efficiency (the ratio of the number of photons pumped to the upper energy level of the laser to the number of photons pumped to the pump band). and This represents the maximum intensity and normalized field distribution occurring on the CMOS. Taking the target moving along the Y-axis as an example, assuming that signal-induced photoelectrons are far more numerous than noise-induced photoelectrons, the estimation error can be approximated as...

[0090]

[0091] Next, we specify the noise in the CMOS, including the impulse noise caused by the incident laser beam. Reading noise Pixel inherent noise Dark current noise and background light noise In addition, there is impact noise associated with the incident beam. This is equivalent to signal photoelectrons. Therefore, a pixel... The noise variance is described as

[0092]

[0093] Finally, the variance of the estimation error is

[0094]

[0095] Therefore, considering the noise of the CMOS detector, the estimation error along the Y-axis can be obtained, and the estimation error along the X-axis can be calculated in the same way. Finally, we can obtain the estimation error of AoA based on the beam intensity distribution, CMOS responsivity, and noise.

[0096] C. Photoelectric conversion

[0097] This invention integrates a laser photovoltaic cell at the receiver for power conversion from light to electricity. To theoretically analyze the capabilities of wireless charging, we employed... Figure 6 The commonly used photovoltaic equivalent circuit model. A photovoltaic cell is modeled as a circuit with current... A light-induced current source, with a current-carrying... The diodes are connected in parallel. When the external load... When connected to the output terminal of a photovoltaic cell, the current It will be generated on RL, with a voltage of Series resistance in photovoltaic models and parallel resistors This represents material defects and ohmic losses in the battery substrate material, metal conductors, and metal contacts. Finally, the converted charging power... It is expressed by the following formula

[0098]

[0099] in, It's the response rate. It is the reverse saturation current. It refers to the number of batteries connected inside the photovoltaic panel. It is the ideal coefficient of the diode. It is Boltzmann's constant. It is Kelvin temperature. It is electron charge. The key to laser photoelectric conversion analysis using an equivalent circuit model is selecting appropriate parameters, i.e. , , and Generally, these parameters are obtained through a fitting process using measurements of actual products.

[0100] IV. Examples and Numerical Results

[0101] a. Parameter settings

[0102] We present an exemplary system design for verifying the performance of the DCCL system, with its CRR parameters and gain medium parameters specified in Table I. In our setup, we assume the receiver FoV is sufficiently large to not be a major limiting factor for the overall system FoV. The theoretical focal length of CRR4 is 100°, while the theoretical focal lengths of CRR1 and CRR2 are the same, approximately 40°. We can then investigate how various focal lengths of CRR3 affect the overall focal length of the DCCL system. For gain simulation, we choose a thin-film Nd:YVO4 gain medium. To demonstrate the integrated power transfer and positioning performance of the proposed system, we employ an equivalent photovoltaic cell model, with parameters obtained by fitting measurements from actual products of MH GoPower's laser photovoltaic panels. The CMOS parameters are selected based on the DCCL simulation. Detailed parameters for integrated power transfer and positioning are given in Table II.

[0103] Table 1. System parameters used in the simulation verification of DCCL

[0104] Table 2. Detailed parameters of the integrated energy transfer and positioning system.

[0105] b. Performance improvements

[0106] We will first introduce the performance improvement brought about by the design of DCCL. Figure 7 The output laser power P of the DCCL is described. out The relationship with R2 and R4. Similar to the DSCL system, the output coupler has an optimal reflectivity for maximum laser power output. Figure 7In (a), as R4 increases, P out First increase, then decrease, and the optimal reflectivity can be determined. Simultaneously, as R² increases, P... out This is also increasing, providing guidance for optimizing the reflectivity of the CRR to achieve higher system performance. Figure 7 In (b), we can obtain the optimal P when R4 = 0.7. out To obtain the optimal P, R2 should be set to 0.7, while R4 should be set to 0.5. out R2 should be set to 0.8. This shows that we can carefully design R2 and R4 for specific application scenarios. Numerical results indicate that selecting appropriate R2 reflectivity and external cavity reflectivity R4 can improve the transmission efficiency of intracavity laser.

[0107] Then, we analyze how DCCL-based systems outperform DSCL-based systems. Figure 8 The output Pout and pump power P of the DCCL system are shown. in The relationship between the transmission distance d along the Z-axis and the transmission distance d was established and compared with that of a DSCL-based system. Assuming both systems have the same CRR configuration in the transceivers and the same d = 2m, the laser in the DSCL system at P... in Laser excitation begins at a power greater than 230W, while the threshold pump power of the DCCL system is only around 35W (at which point laser excitation is possible). Feedback from the external resonant cavity significantly reduces the threshold pump of the main resonant cavity, improving the system's energy transfer efficiency. For example... Figure 8 As shown, the maximum achievable Z-axis transmission distance d of the DSCL system is less than 5 meters, while the achievable Z-axis transmission distance d of the DCCL system is about 23 meters. Similar conclusions can be drawn through simulation analysis of the output laser power increasing with d.

[0108] Figure 9 Showing P under different CRR3 designs out The relationship between the transmitter FoV (determined by different focal lengths f3 of L3) and the transmitter FoV. Figure 8 We selected P for the DCCL system. in =100W, select P for DSCL system in =250W. The image shows that the DSCL system requires a focal length of... f When 3mm is set to 30mm (black line), the transmitter's FoV can reach ±20◦. However, in a DCCL system, even at... f When 3=10mm, the typical FoV of its transmitter can also reach ±50◦ (green line).

[0109] In summary, the DCCL design achieves improved energy transfer efficiency and FoV, which may provide higher system performance for SWIPT and positioning.

[0110] c. Positioning accuracy

[0111] Figure 10 The AoA estimation accuracy of the proposed DCCL-powered positioning integrated system is shown, where we select P in =100W and d=2m. We use formula (11) to show the standard deviation of the error of the mass estimation of the beam on the CMOS. The simulation only considers the Y-axis motion of the receiver and various noises caused on the CMOS. It can be seen that the AoA estimation accuracy will stabilize at a high level within the FoV range of the system. It can also be seen that the AoA estimation accuracy will decrease as the noise on the CMOS increases. However, at low noise, i.e., below 50e (e represents the basic charge) shown in this simulation, the AoA estimation of the remote receiver can easily achieve millimeter-level accuracy. In addition, the measurement results from the existing PSM-based laser ranging test bench show that millimeter-level ranging accuracy has been achieved.

[0112] d. Charging power

[0113] We also demonstrated the WPT wireless power transfer performance of the DCCL-Power Transfer and Positioning Integrated System, such as... Figure 11 In P in With a power rating of 100W and a d=2m, the wireless power transmission should be greater than 4W to meet the requirements of watt-level power IoT. Figure 11 As can be seen, with F3=10mm, the system can achieve a charging power of 4W within ±40◦FoV, which can meet the power supply requirements of most IoT devices. The numerical results above show that the DCCL-based system outperforms the DSCL-based system in terms of energy transfer efficiency and FoV.

[0114] V. Conclusion

[0115] In this invention, we propose the design of a DCCL-powered positioning integrated system. First, we highlight the mechanisms for enhancing the power transfer efficiency and FoV of the DCCL system. Then, by exploring the self-alignment and self-mixing effects of DCCL-based PSM, we achieve AoA estimation based on spot position acquisition and distance estimation based on coupled-cavity PSM ranging, integrating these two functions to achieve 3D positioning. Simultaneously, we integrate a photovoltaic (PV) cell in the receiver to convert intracavity laser power into electrical energy. Finally, simulation results show that the DCCL-powered positioning integrated system can simultaneously achieve watt-level wireless charging and millimeter-level positioning at transmission distances of ±40° and 2m, while also improving the system's field of view.

[0116] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A cavity laser energy transfer and positioning integrated system based on a coupled-cavity laser, characterized in that, It includes a transmitter and a receiver integrated into a remote user equipment, and a main resonant cavity composed of components in the transmitter and receiver, as well as a free-space resonant cavity coupled to the main resonant cavity; The main resonant cavity is located in the transmitter and is used to generate intracavity laser. It consists of a first retroreflector, a gain medium, and a second retroreflector arranged sequentially along the optical path. The gain medium is connected to the pump source. The free-space resonant cavity consists of a third retroreflector integrated in the transmitter and a fourth retroreflector integrated in the receiver for providing effective optical frequency electromagnetic field feedback. The third retroreflector and the second retroreflector are beam-coupled to each other. The transmitter is also equipped with: a beam-capturing unit for estimating the angle of arrival (AoA), a ranging unit, and a microcontroller unit that receives the AoA estimation and ranging results and obtains the positioning information respectively; The ranging unit performs ranging based on the self-mixing characteristics and inherent polarization modulation of DCCL. The intracavity laser of the main resonant cavity maintains two linear polarization modes. A polarization rotator is placed between the third and fourth retroreflectors to induce polarization mode switching. A beam-splitting mirror M is placed between the polarization rotator and the third retroreflector. The portion of the reverse beam separated by the beam-splitting mirror M is collected by a Wollaston prism and separated into two polarization components. The intensity of one component is detected by a photodiode and sent to a spectrum analyzer to find the polarization self-modulation spectrum. The other component is collected by another photodiode and sent to a frequency counter controlled by a computer PC. The length of the spatial resonant cavity... Depend on Determine, by determining the frequency switching period t estimate d : In the formula, At the speed of light, The switching frequency is the frequency at which the reflected beam is reflected back by the fourth retroreflector.

2. The integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser according to claim 1, characterized in that, The beam capturing unit includes a CMOS image sensor disposed at the end of the first retroreflector away from the second retroreflector for capturing the beam; the CMOS image sensor is connected to a microcontroller unit.

3. The integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser according to claim 2, characterized in that, The AoA estimation steps include: The light field distribution on the CMOS image sensor is obtained, the position of the light spot on the CMOS image sensor is obtained according to the centroid algorithm, and the position of the target is determined by the position of the light spot on the CMOS image sensor; the estimation error of the angle of arrival (AoA) is obtained according to the beam intensity distribution, CMOS responsivity and noise; and then the estimated angle of arrival (AoA) is obtained.

4. The integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser according to claim 3, characterized in that, The CMOS image sensor obtains photoelectrons on each pixel. This includes the electrical power converted from the incident laser beam and the noise power on the CMOS sensor: in, and These are photoelectrons caused by the loading signal and noise on the intracavity laser, respectively. It refers to the CMOS responsivity. It is quantum efficiency; and It represents the maximum intensity and normalized field distribution occurring on the CMOS. The estimation error of AoA is obtained based on beam intensity distribution, CMOS responsivity, and noise. Wherein, the variance of the estimation error along the Y-axis The expression is as follows: in, This refers to the noise variance in CMOS. It is the index value of the CMOS pixel.

5. The integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser according to claim 4, characterized in that, The noise variance in the CMOS includes the impulse noise caused by the incident laser beam. Reading noise Pixel inherent noise Dark current noise and background light noise Pixels The noise variance is expressed as: in, It is photoelectrons caused by noise on the intracavity laser; It is the CMOS responsivity; and It represents the maximum intensity and normalized field distribution occurring on CMOS.

6. The integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser according to claim 1, characterized in that, The receiver integrates a photovoltaic cell for converting intracavity laser light into electrical energy.

7. The integrated intracavity laser energy transfer and positioning system based on a coupled-cavity laser according to claim 1, characterized in that, The coupled cavity laser operates under a high threshold condition by setting the reflectivity of the second and third retroreflectors, thus preventing the main resonant cavity from independently generating laser light after being pumped by a pump source.

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