Laser alarm based on silicon photonics chip

Abstract

This invention discloses a laser alarm, comprising an optical receiving system, an optical scanning system, an optical switch, an optical amplification system, a wavelength division detection system, and a signal processing system. The optical system receives incoming laser light and transmits it to the optical scanning system. The optical scanning system uses a micro-mirror to perform the scanning. After passing through the optical switch, visible light signals directly enter the wavelength division detection system, while near-infrared light signals are amplified before entering the system. In this design, the optical switch, optical amplification system, and wavelength division detection system are integrated onto a single silicon photonic chip, including a silicon-based waveguide switch, a silicon-based waveguide amplifier, an arrayed waveguide grating, and a silicon-based photodetector. The signal processing system is connected to the micro-mirror chip and the silicon-based photodetector acquisition card. This invention achieves miniaturization of the laser alarm, enabling rapid detection of threatening laser signals and acquisition of laser azimuth and wavelength information, with high directional accuracy and a low false alarm rate.

Description

Technical Field

[0001] This invention relates to a laser alarm, and more particularly to a method for constructing a laser alarm system using a silicon photonic chip with micro-mirror scanning, optical amplification, and wavelength division. Background Technology

[0002] Laser warning receivers, as a specialized reconnaissance method, can rapidly and accurately identify laser threat signals, determine their location and threat level, and issue warning signals within a wide field of view. They offer advantages such as a large real-time detection range, wide bandwidth, simple maintenance, and small footprint, making them a crucial component of optoelectronic countermeasures technology. They are typically fixed to important facilities such as aircraft, armored vehicles, and satellites. In recent years, countries like the United States and Russia have conducted extensive research on laser warning receivers, resulting in significant improvements in detection accuracy, resolution, field of view, and sensitivity. Based on their detection principles, laser warning receivers are mainly classified into three types: imaging-based, spectral recognition-based, and coherent recognition-based.

[0003] Coherent recognition laser alarms utilize the principle of temporal coherence of laser height for detection and are easy to filter non-laser signals. They have advantages such as a large detection field of view, high angular resolution, and the ability to detect laser wavelengths. However, they are complex in structure, have poor anti-interference ability, and are technically difficult to use, so they have no practical applications.

[0004] Spectral recognition type mainly consists of a signal detection device and an information processing device. It usually uses photodiodes as detection elements and determines the threat level of incoming lasers through amplification and signal processing. It has the advantages of good detection effect on pulsed lasers, simple system structure, and high sensitivity. It has a wide range of applications and mature technology. However, it also has the problems of low accuracy and complex processing circuits.

[0005] Imaging laser warning devices typically consist of a large field-of-view optical system and a charge-coupled device (CCD) array. They do not require mechanical scanning and have advantages such as high spatial angular resolution, high sensitivity, and large dynamic range. However, CCDs have low readout frame rates, poor detection capability for pulsed light, high cost, and complex image processing technology, resulting in limited applications.

[0006] The above three types of laser warning devices generally suffer from problems such as large size, high energy consumption, limited functionality, and insufficient directional accuracy. With the development of laser weapons and laser detection equipment, traditional laser warning devices can no longer meet the needs of modern military operations. Summary of the Invention

[0007] The purpose of this invention is to provide a laser alarm device to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A laser alarm based on a silicon photonics chip is characterized by comprising an optical receiving system, a micro-mirror scanning system, a silicon-based waveguide switch, a silicon-based waveguide amplifier, a wavelength division detection system, and a signal processing system.

[0010] The optical receiving system is used to receive the laser beam, focus it, and transmit it to the micro-mirror scanning system;

[0011] The micro-mirror scanning system is used to receive the focused beam transmitted by the optical receiving system and couple it to an optical fiber;

[0012] The silicon-based optical waveguide switch is connected to the micro-mirror scanning system and is used to split the incident light from the optical fiber into two paths: one path is in the visible light band and is connected to the wavelength division detection system; the other path is in the near-infrared light band and is connected to the wavelength division detection system after passing through the silicon-based waveguide amplifier.

[0013] The silicon-based waveguide amplifier is used to amplify the optical energy of near-infrared signals.

[0014] The aforementioned wavelength division detection system is used to divide the optical signal into multiple channels for detection, and to obtain information on the wavelength and signal power of the incoming laser.

[0015] The signal processing system is connected to the micro-mirror scanning system and the wavelength division detection system to acquire threatening laser signals as well as information on the wavelength and azimuth of the incoming laser.

[0016] Preferably, the optical receiving system consists of a beam expander or a focusing lens.

[0017] Preferably, the micro-mirror is an electrostatic MEMS micro-scanning mirror, compatible with CMOS technology.

[0018] Preferably, the optical switch is a silicon-based waveguide optical switch.

[0019] Preferably, the silicon-based waveguide amplifier is a silicon-based integrated III-V semiconductor laser amplifier.

[0020] Preferably, the arrayed waveguide grating is a multimode output waveguide arrayed waveguide grating (MM-AWG).

[0021] As a further aspect of the present invention: the silicon-based photodetector adopts a Si-PIN germanium-silicon detector array.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] By utilizing a micro-mirror and a silicon photonic chip with optical switching, optical amplification, and wavelength division detection, the laser alarm device has been miniaturized, highly integrated, and its energy consumption has been greatly reduced. It can also perform high-speed simultaneous measurement of the wavelength and azimuth of incoming lasers, detect threatening lasers in a short time, has a low false alarm rate, and high angular resolution. Attached Figure Description

[0024] Figure 1 This is a structural block diagram of the laser alarm device based on silicon photonics chip according to the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of an embodiment of the laser alarm device based on silicon photonics chip of the present invention.

[0026] Figure 3 This is a schematic diagram of the micro-mirror scanning of the present invention.

[0027] Figure 4 This is a schematic diagram of a silicon-based optical waveguide switch. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0029] Please see Figure 1 In this embodiment, the laser alarm includes an optical receiving system, a micro-mirror scanning system, a silicon-based waveguide switch, a silicon-based waveguide amplifier, a wavelength division detection system, and a signal processing system.

[0030] The optical system receives the incoming laser, transmits it to the micro-mirror for scanning, and then sends it to the silicon-based optical waveguide switch after reflection. One path goes directly to the wavelength division detection system, while the other path is amplified by the silicon-based waveguide before being sent to the wavelength division detection system. The signal processing system connects the optical scanning system and the wavelength division detection system to obtain the laser signal with a threat signal, as well as the wavelength and azimuth information of the incoming laser.

[0031] See Figure 2The optical receiving system consists of a focusing lens / beam expander 1, which is used to collect incoming laser light and focus it. The optical scanning system consists of a scanning MEMS 2 and a micro-mirror control chip. Under the control of the micro-mirror drive chip, the micro-mirror swings rapidly along the axis to scan, receive the focused beam of the focusing lens / beam expander 1, and reflect it into the fiber laser coupler (3). The fiber laser coupler 3 couples the spatial light reflected by the micro-mirror into the optical fiber, and then transmits the light to the silicon photonic chip through end-face coupling. The field of view of the optical receiving system is determined by the scanning field of view of the micro-mirror, and the field of view of the two are the same. After the optical signal enters the silicon photonic chip, it is first transmitted to the silicon-based optical waveguide switch 4 and divided into two paths. One path is a visible light signal light, which directly enters the wavelength division detection device for detection. The other path is a near-infrared signal light, which is amplified by an amplifier and then divided for detection. The optical amplification is performed by a silicon-based III-V semiconductor laser amplifier 5 and a wavelength division detector 6. The wave detection system consists of a multimode output waveguide array (MM-AWG) 6 and a Si-PIN germanium silicon detector array 7. Using silicon as the substrate, and employing silicon CMOS technology, four devices—a silicon-based optical waveguide switch (4), a silicon-based III-V semiconductor laser amplifier (5), a multimode output waveguide array (MM-AWG) 6, and a Si-PIN germanium silicon detector array 7—are integrated onto a single silicon photonic chip. This achieves optical channel separation, optical amplification, wave division, and detection functions. The silicon-based integrated III-V semiconductor laser amplifier utilizes… Using bonding technology, a traditional semiconductor laser amplifier (SOA) is attached to a substrate, providing a wide amplification wavelength coverage and enabling broadband optical amplification. Amplification of the optical signal effectively improves the system's detection sensitivity and facilitates subsequent signal processing. A multimode output waveguide array with waveguide gratings can simultaneously cover multiple bands, with a total of 8 channels, effectively splitting the optical signal. The Si-PIN germanium-silicon detector has a dark current of only nA, enabling the detection of light with wavelengths less than 1.87μm, while maintaining a responsivity at -1V bias at 1550nm and 1... The 310nm wavelengths are 0.72A / W and 0.98A / W respectively, with good 3dB bandwidth, meeting the detection requirements; the signal processing circuit board 8 connects the micro-mirror scanning system and the detector acquisition card. When all eight channels of the signal processing circuit board have zero signals or have signals that are similar, the incoming laser has not been detected; if a single detector has an output signal and the signals of other detectors are zero or weak, the incoming laser has been detected, and the wavelength of the incoming laser is obtained from the detector with the output signal, and the azimuth angle of the incoming laser is obtained by combining it with the galvanometer vibration signal.

[0032] Figure 3 The image shows a scanning diagram of a micro-mirror. The dashed line represents the mirror's rotation axis. The mirror rapidly scans along the axis to send incident light at different angles into the fiber coupler.

[0033] Figure 4This is a silicon-based optical waveguide switch. Two waveguides, each with a width of w, intersect at an angle θ to form an X-shaped structure. r The length is L r The reflection zone is located in the intersection area. Incident light enters from port I1. Due to external factors, the refractive index of the reflection zone changes. The light input from port I1 is reflected to port I4 (reflection state). Otherwise, the light spot is directly transmitted to port I3, thus realizing the function of optical switch.

[0034] The specific parameters of the system are determined as follows:

[0035] 1) Determine the focusing lens aperture

[0036] Assume the laser emission power is p t The received power on the detector is p r The detector's signal-to-noise ratio (SNR) is given by the formula for detection.

[0037]

[0038] In the formula, t0 is the one-way atmospheric transmittance, t T T represents the transmittance of the transmission system. r R is the transmittance of the receiving system, R is the target distance, and θ is the transmittance of the receiving system. t It is the laser divergence angle, A r This refers to the receiver aperture area. In a space environment, with a detection range of 5000km, a laser emission power of 25W, a laser divergence angle of 100μrad, atmospheric transmittance, and transmittance of both the transmitting and receiving systems (1), and a minimum detection power of 10μW, the receiver aperture area A can be calculated using the formula. r The minimum is 0.079㎡.

[0039] 2) Determine the scanning field of view and angular resolution

[0040] Assuming a vertical field of view of 30°, the scanning angular resolution mainly depends on the maximum scanning angle of the micromirror, its resonant frequency, and the system scanning frequency. The formula for the vertical angular resolution is as follows:

[0041]

[0042] Where R v For vertical angular resolution, S v Where f is the vertical field of view, P is the system scanning frequency, and f is the vertical field of view. v The resonant frequency of the micromirror is given. The mirror scanning angle is determined by the initial incident beam and the mirror rotation angle, satisfying the following formula:

[0043] Φ=cos -1 (1-2cosθ 2 sin2α 2 )

[0044] Where Φ is the galvanometer scanning angle, θ is the initial incident angle, and α is the galvanometer rotation angle. However, after setting a specific initial incident angle, the galvanometer scanning angle is determined by the galvanometer rotation angle. With an initial incident angle θ = 0°, the incident beam is perpendicular to the galvanometer rotation axis, and the above equation can be transformed into...

[0045] cosΦ=1-2cosθ 2 sin2α 2 =cos4α

[0046] That is, Φ = 4α, at which point the total deflection angle of the galvanometer is 2α, and the scanning angle is twice the total deflection angle of the galvanometer. However, when the initial incident angle θ ≠ 0°, the scanning angle is affected by both the incident angle and the galvanometer rotation angle, and the scanning angle Φ < 4α. When the initial incident angle is determined, the scanning angle increases with the increase of the galvanometer rotation angle; when the galvanometer rotation angle is determined, the scanning angle decreases with the increase of the initial incident angle. To make full use of the galvanometer rotation angle and obtain the maximum scanning angle, the initial angle is determined to be 0°, and the emitted beam exits perpendicular to the galvanometer rotation axis.

[0047] 3) Micromirror driving signal

[0048] This driving signal is a current signal, typically a sinusoidal signal. The current and voltage characteristics of this signal are determined by the electrical signal of the micromirror used. Its frequency is equal to the resonant frequency f of the MEMS scanning mirror. v .

[0049] 4) Data acquisition signal

[0050] The circuit board reads the real-time signals from multiple Si-PIN germanium silicon detectors, and the readout frequency is the same as the resonant frequency of the micromirror.

[0051] This invention can quickly detect threatening incoming lasers, as well as their azimuth and wavelength information. It has a low false alarm rate and high angular resolution. Furthermore, by utilizing a micro-mirror and a silicon photonic chip with optical switching, optical amplification, wavelength division, and detection capabilities, the size of the laser alarm is greatly reduced, achieving miniaturization. This invention plays an important role in the security protection of critical equipment in the military.

Claims

1. A laser alarm device based on a silicon photonics chip, characterized in that, It includes an optical receiving system, a micro-mirror scanning system, a silicon-based waveguide switch, a silicon-based waveguide amplifier, a wavelength division detection system, and a signal processing system; The optical receiving system is used to receive the incoming laser, focus it, and transmit it to the micro-mirror scanning system; The micro-mirror scanning system is used to receive the focused beam transmitted by the optical receiving system and couple it to an optical fiber; The silicon-based waveguide switch is connected to the micro-mirror scanning system and is used to split the incident light from the optical fiber into two paths: one path is in the visible light band and is connected to the wavelength division detection system; the other path is in the near-infrared light band and is connected to the wavelength division detection system after passing through the silicon-based waveguide amplifier. The silicon-based waveguide amplifier is used to amplify the optical energy of near-infrared signals. The aforementioned wavelength division detection system is used to divide the optical signal into multiple channels for detection, and to obtain information on the wavelength and signal power of the incoming laser. The signal processing system is connected to the micro-mirror scanning system and the wavelength division detection system to acquire threatening laser signals as well as information on the wavelength and azimuth of the incoming laser. The size of the light spot imaged onto the micromirror by the optical receiving system is equal to the mirror surface size; the field of view is 30°, and the specific parameters of the optical system are calculated as follows: The laser emission power is P t The receiving power on the detector is P r The detector's signal-to-noise ratio (SNR) is given by the formula for detection. In the formula, T0 is the one-way atmospheric transmittance, and T t T represents the transmittance of the transmission system. r R is the transmittance of the receiving system, R is the target distance, and θ is the transmittance of the receiving system. t It is the laser divergence angle, A r This refers to the receiving aperture area. In a space environment, with a detection range of 5000km, a laser emission power of 25W, a laser divergence angle of 100μrad, atmospheric transmittance, and transmittance of both the transmitting and receiving systems (1), and a minimum detection power of 10μW, the receiving aperture area A can be calculated using the formula. r The minimum is 0.079㎡.

2. The laser alarm device based on a silicon photonic chip according to claim 1, characterized in that, The micromirror scanning system includes a MEMS micromirror and a driving module.

3. The laser alarm device based on a silicon photonic chip according to claim 1, characterized in that, The aforementioned wavelength division detection system consists of a silicon-based arrayed waveguide grating and a silicon-based photodetector array. The optical signal is divided by the arrayed waveguide grating and then received and detected by the photodetector array.

4. The laser alarm device based on a silicon photonic chip according to claim 1, characterized in that, The optical receiving system consists of a beam expander or a focusing lens, and the field of view of the optical receiving system is the same as that of the micro-mirror scanning system.

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