Quantum electromagnetic field sensors and imagers

Abstract

A sensor is disclosed, comprising a vapor chamber containing vapor of alkali atoms. The sensor further comprises a first photonic integrated circuit (PIC) configured to direct light of a first wavelength into the vapor chamber and incident on the vapor of the alkali atoms, wherein the light of the first wavelength is configured to excite the alkali atoms from a ground state to a first excited state. The sensor further comprises a detector configured to detect a response of the alkali atoms to incident electromagnetic radiation after the alkali atoms are excited from the first excited state to a Rydberg state.

Description

[0001] Related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 991,999, filed on March 19, 2020, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to imaging devices. Background Art

[0004] Image sensors can be semiconductor devices used to convert electromagnetic radiation into electrical signals. Examples include charge-coupled devices (CCDs), complementary metal semiconductor (CMOS) devices, photodiode arrays, charge injection devices, hybrid focal plane arrays, etc. For electromagnetic radiation in the terahertz (THz) frequency range, such as millimeter waves, conventional imagers can include microbolometers, photoconductive devices, folded dipole antennas, Schottky barrier diodes, pyrometry devices, and Golay detectors, such as photoacoustic detectors. Summary of the Invention

[0005] Generally speaking, the present disclosure describes sensor arrays for imaging electromagnetic (EM) radiation having frequencies in the megahertz (MHz), gigahertz (GHz), and terahertz (THz) ranges (MHz / GHz / THz EM radiation). In some examples, a vapor cell array can be used as a transducer to convert electromagnetic radiation having frequencies in a first range into electromagnetic radiation having frequencies in a second range. In some examples, the electromagnetic radiation in the second frequency range can be more easily discerned, have a higher signal-to-noise ratio (SNR), can be less expensive to detect, can be detected by a smaller or lighter device, and have higher sensitivity than directly detecting the electromagnetic radiation in the first range.

[0006] In some examples, the vapor chamber array can include a plurality of vapor chambers containing alkali atoms. The alkali atoms can be prepared into a Rydberg state, wherein the alkali atoms are excited so that one or more electrons have a very high principal quantum number n. The alkali atoms in the Rydberg state can have loosely bound valence electrons, which may be disturbed or ionized by collisions or external fields (such as MHz / GHz / THz radiation). In some examples, the alkali atoms in each vapor chamber of the vapor chamber array can be prepared by coupling light with a first frequency and excitation with a probe light with a second frequency. In some examples, the frequency of one or both of the coupled light and the probe light can be ultraviolet, visible or near infrared (UV / VIS / NIR) frequency. The probe light can excite the alkali atoms from the first quantum energy level to the second quantum energy level, and the coupled light can excite the alkali atoms from the second quantum energy level to the third quantum energy level, so that the alkali atoms are in a Rydberg state.

[0007] In some examples, alkali atoms in Rydberg states can exhibit electromagnetically induced transparency (EIT) for frequencies close to the frequency of a probe light. The probe light can be configured to be detected by a detector array after being transmitted through vapor cells of a vapor cell array. Perturbations of the alkali atoms in the Rydberg states by EM radiation in the MHz / GHz / THz frequency range can be detected via shifts in the EIT spectral window of the probe light, which is transmitted through the vapor cell array to the detector array, thereby generating a signal of the probe light in the UV / VIS / NIR frequency range that is proportional to the amplitude and frequency of the EM radiation in the MHz / GHz / THz frequency range.

[0008] In some examples, the imaging system includes a vapor cell array and a detector array.Probe light and coupled light in the UV / VIS / NIR frequency range can be used to image incident electromagnetic radiation in the MHz / GHz / THz frequency range.

[0009] Thus, these techniques can provide one or more technical advantages that enable at least one practical application. For example, these techniques can improve the sensitivity and signal-to-noise ratio (SNR) of MHz / GHz / THz electromagnetic radiation imaging systems. These techniques can also reduce the size, weight, and power (SWaP), as well as the cost, of MHz / GHz / THz electromagnetic radiation imaging systems.

[0010] In some examples, the present disclosure describes a sensor comprising a vapor chamber having vapor of alkali atoms, a first photonic integrated circuit (PIC) configured to direct light of a first wavelength into the vapor chamber and incident on the vapor of alkali atoms, wherein the light of the first wavelength is configured to excite the alkali atoms from a ground state to a first excited state, and a detector configured to detect a response of the alkali atoms to the incident electromagnetic radiation after the alkali atoms are excited from the first excited state to a Rydberg state.

[0011] In some examples, the present invention describes a method comprising exciting alkali atoms in a vapor chamber from a first quantum state to a second quantum state via light of a first wavelength from a first photonic integrated circuit (PIC), exciting alkali atoms in a plurality of vapor chambers to Rydberg states via light of a second wavelength, detecting a response of the alkali atoms in the Rydberg states to incident electromagnetic radiation, and outputting a signal proportional to the detected response.

[0012] In some examples, the present invention describes an electromagnetic radiation detection array comprising a plurality of vapor chambers arranged in a two-dimensional (2D) array, each vapor chamber comprising an alkali atom gas, a first photonic integrated circuit (PIC) configured to direct light of a first wavelength into each vapor chamber of the plurality of vapor chambers and incident upon the vapor of the alkali atoms, wherein the light of the first wavelength is configured to excite the alkali atoms from a ground state to a first excited state; a second PIC configured to direct light of a second wavelength into each vapor chamber of the plurality of vapor chambers and incident upon the vapor of the alkali atoms, wherein the light of the second wavelength is configured to excite the alkali atoms from the first excited state to a Rydberg state, and a plurality of detectors, each detector corresponding to one vapor chamber of the plurality of vapor chambers and configured to detect a response of the alkali atoms in the Rydberg state to the incident electromagnetic radiation.

[0013] The details of one or more examples of the technology of the present disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of these technologies will become apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a cross-sectional block diagram illustrating an example imaging system in accordance with techniques of this disclosure.

[0015] Figure 2A is a perspective view of an example vapor chamber array in accordance with the presently disclosed technology.

[0016] Figure 2B is a perspective diagram showing a partially transparent block diagram of an example imaging system 160 in accordance with techniques of this disclosure.

[0017] Figure 3 is a cross-sectional view of an example sensor according to the techniques of this disclosure.

[0018] Figure 4 is a cross-sectional view of an example sensor according to the techniques of this disclosure.

[0019] Figure 5 is a flow chart of an example method of imaging electromagnetic radiation in accordance with the techniques of this disclosure.

[0020] Figure 6 is an illustration of an example energy diagram for an alkali atom including at least one Rydberg state in accordance with the presently disclosed techniques.

[0021] Figure 7 is an example graph showing the absorption signal response of the probe light as a function of the probe light frequency detuning according to the techniques of this disclosure.

[0022] Figure 8 is an illustration of an example energy diagram for an alkali atom including at least one Rydberg state in accordance with the presently disclosed techniques.

[0023] Figure 9 is a block diagram of an example system 900 for sensing EM radiation in accordance with the techniques of this disclosure.

[0024] Figure 10 is a cross-sectional view of an example sensor according to the techniques of this disclosure.

[0025] Figure 11 is a cross-sectional view of an example sensor according to the techniques of this disclosure.

[0026] Figure 12 is a flow chart of an example method of imaging electromagnetic radiation in accordance with the techniques of this disclosure.

[0027] Like reference characters refer to like elements throughout the drawings and the description. DETAILED DESCRIPTION

[0028] Terahertz (THz) radiation can be used for a range of different applications, such as telecommunications and wireless networks (using millimeter wave mobile broadband systems), antenna and advanced radar applications, environmental monitoring, counter-terrorism, astronomical observations such as with small satellites and CubeSats, characterizing materials, characterizing electromagnetic interference, medical testing, and microwave background detection. Some of the advantages of THz radiation are its low energy distribution and its non-ionizing distribution, making it relatively harmless.

[0029] There are many possible applications for using terahertz detectors and imagers. For example, terahertz detectors can be integrated into self-calibrated electric field and power sensors in the radio frequency (RF), microwave, and millimeter wave ranges, such as high-energy applications with electric fields greater than 1 kilovolt / meter (kV / m). In the security field, terahertz imaging can be used to detect concealed cargo or weapons. Millimeter wave imagers can be used in aviation applications; for example, monitoring the movement of aircraft on the ground in adverse weather conditions. In addition, millimeter wave sensors can be applied to biosensing to monitor vital signs at large standoff distances.

[0030] Figure 1 is a cross-sectional block diagram illustrating an example imaging system 100 in accordance with techniques of the present disclosure. In the illustrated example, imaging system 100 includes a vapor cell array 102, a detector array 104, a first waveguide 106, a second waveguide 108, imaging optics 110, and a computing device 120. Imaging system 100 may also include a coupled light source 130 and a probe light source 140. Figure 1 Also shown are processing circuitry 116 communicatively coupled to imaging system 100 and memory 124 communicatively coupled to processing circuitry 116. Figure 1 The cross-sectional view of imaging system 100 in FIG. 1 shows imaging system 100 in one dimension (1D), but imaging system 100 can be a two-dimensional (2D) system, for example, vapor chamber array 102, detector array 104, first waveguide 106, and second waveguide 108 can be two-dimensional arrays including multiple individual elements in the x-direction and the y-direction, such as detector 114 and vapor chamber 112.

[0031] The vapor chamber array 102 may include a plurality of vapor chambers 112, each vapor chamber 112 including atomic vapor, such as alkali atoms. Figure 1 The cross-sectional view illustrates the vapor chamber array 102 as a 1D array including a plurality of vapor chambers 112 in the y-direction, but the vapor chamber array 102 can be a 2D array including a plurality of vapor chambers 112 in both the x-direction and the y-direction. In some examples, each vapor chamber 112 is configured as a transducer that converts electromagnetic radiation having a frequency within a first range into electromagnetic radiation having a frequency within a second range. For example, each vapor chamber 112 can transduce or convert electromagnetic radiation 152 having a frequency in the megahertz (MHz), gigahertz (GHz), and terahertz (THz) ranges (MHz / GHz / THz radiation 152) into optical frequencies in the picohertz (PHz) range. In terms of wavelength, each vapor chamber 112 can convert electromagnetic radiation in the meter to millimeter wavelength range into electromagnetic radiation in the UV / VIS / NIR wavelength range.

[0032] In some examples, each vapor cell 112 may include atomic vapor configured to exhibit electromagnetically induced transparency (EIT). For example, the alkali atoms in each vapor cell 112 may be prepared in a Rydberg state by driving the alkali atoms from a first quantum energy level to a higher second quantum energy level via probe light 142 and further driving the alkali atoms from the second quantum energy level to a higher third quantum level via coupling light 132, as described below with respect to Figure 6 Further explanation and description of the invention. In the presence of strongly resonant coupled light 132, for example, coupled light 132 having a frequency that closely matches the energy gap between the second quantum state and the third quantum state, the refractive index of the vapor of the alkali atoms in the vapor cell 112 can be modified for frequencies close to the frequency of the probe light 142, resulting in an EIT window in the absorption spectrum of the alkali atoms near that frequency, for example, the frequency of the probe light 142. Thus, the absorption spectrum of the alkali atoms can be observed as a function of the frequency detuning of the probe light 142, as described below with respect to Figure 7 Further explained and described.

[0033] The EIT transparency window can have a spectral width of less than 1 MHz, less than 10 MHz, or less than 100 MHz, and can allow for sub-Doppler accuracy in measuring the response of alkali atoms to MHz / GHz / THz electromagnetic radiation at room temperature. For example, perturbations in the energy level of the alkali atoms in the third quantum level (e.g., Rydberg state) can be measured by changes in the EIT window detected by the intensity of the probe light 142 at the detector array 104. In other words, each alkali atom can act as an independent transducer that converts incident MHz / GHz / THz electromagnetic radiation into an optical signal, and the alkali atom clusters of the vapor cell 112 can incoherently amplify the optical signal.

[0034] In some examples, probe light 142 may be UV / VIS / NIR light. For example, probe light 142 may be a 780 nm laser, and probe light source 140 may be a 780 nm laser. In some examples, coupling light 132 may be UV / VIS / NIR light. For example, coupling light 132 may be a 480 nm laser, and coupling light source 130 may be a 480 nm laser.

[0035] The first waveguide 106 can be configured to transmit and extract the coupled light 132 to one or more vapor cells 112. In some examples, the first waveguide 106 can be a photonic integrated circuit (PIC) including a waveguide and one or more extraction features. As described above, although Figure 1The cross-sectional view of illustrates the first waveguide 106 as a 2D structure having a height in the y-direction and a thickness in the z-direction, but the first waveguide 106 can be a 3D structure having a height in the y-direction, a width in the x-direction, and a thickness in the z-direction, and can include multiple structural features arranged in the x-direction and the y-direction, such as the vapor chambers 112 corresponding to the 2D vapor chamber array 102. In some examples, the first waveguide 106 can be configured to transmit the coupled light 132 via total internal reflection (TIR) ​​to distribute the coupled light 132 over a 2D area, and extract the coupled light 132 via extraction features on a front surface or a back surface, for example, a surface in the xy plane or within the first waveguide 106. In some examples, the extraction features can be configured to prevent TIR and guide the coupled light 132 from a predetermined position of the first waveguide 106 in a predetermined direction, for example, toward one or more vapor chambers 112. In some examples, the coupling light source 130 can inject the coupled light 132 into one or more edges of the first waveguide 106, such as Figure 1 As shown. In other examples, the first waveguide 106 can be an optical element having optical power, such as a lens or lenslet array, a diffraction grating, or any optical element configured to guide the coupled light 132 to the vapor cell 112 of the vapor cell array 102. In some examples, the first waveguide 106 may not be a waveguide that transmits the coupled light 132 via TIR, but may be any other structure configured to guide the coupled light 132 from a predetermined position of the first waveguide 106 in a predetermined direction, such as a beam splitter array. In some examples, the system 100 may include a plurality of coupled light sources 130, for example, distributed along one or more edges of the first waveguide 106 and configured to inject coupled light into one or more edges of the first waveguide 106. In some examples, the coupled light sources 130 can inject coupled light into the first waveguide 106 via any surface and at any location of the first waveguide 106, for example, via a coupling structure that emits light into any surface of the first waveguide 106 and is configured to guide the coupled light into the first waveguide 106 for transmission.

[0036] The second waveguide 108 can be configured to transmit and extract the probe light 142 through the vapor cell array 102 to the detector array 104. In some examples, the second waveguide 108 can be a PIC comprising a waveguide having one or more extraction features. As described above, although Figure 1The cross-sectional view illustrates the second waveguide 108 as a 2D structure having a height in the y-direction and a thickness in the z-direction, but the second waveguide 108 can be a 3D structure having a height in the y-direction, a width in the x-direction, and a thickness in the z-direction, and can include multiple structural features arranged in the x-direction and the y-direction, such as the vapor chambers 112 corresponding to the 2D vapor chamber array 102 and the detectors 114 of the 2D detector array 104. In some examples, the second waveguide 108 can be configured to transmit the probe light 142 via TIR to distribute the coupled light 132 over a 2D area, and extract the probe light 142 via extraction features on the front or back surface (e.g., a surface in the xy direction) or within the second waveguide 108. In some examples, the extraction features can be configured to suppress TIR and guide the probe light 142 from a predetermined position of the second waveguide 108 in a predetermined direction, for example, through the vapor chamber 112 toward the detector 114. In some examples, the probe light source 140 can introduce the probe light 142 into one or more edges of the second waveguide 108, such as Figure 1 As shown. In other examples, the second waveguide 108 can be an optical element having optical power, such as a lens or lenslet array, a diffraction grating, or any optical element configured to guide the probe light 142 through the vapor chambers 112 of the vapor chamber array 102 to the detectors 114 of the detector array 104. In some examples, the second waveguide 108 may not be a waveguide that transmits the probe light 142 via TIR, but may instead be another structure configured to guide the probe light 142 from a predetermined position of the second waveguide 108 in a predetermined direction, such as a beam splitter array. In some examples, the system 100 may include a plurality of probe light sources 140, for example, distributed along one or more edges of the second waveguide 108 and configured to introduce the probe light into one or more edges of the second waveguide 108. In some examples, the probe light source 140 can introduce coupled light into the second waveguide 108 via any surface and any location of the second waveguide 108, for example, by launching light into a coupling structure located on any surface of the second waveguide 108 and configured to introduce the coupled light into the second waveguide 108 for transmission.

[0037] In some examples, imaging system 100 may include one of first waveguide 106 configured to transmit and extract coupled light 132 or second waveguide 108 configured to transmit and extract probe light 142. In other examples, imaging system 100 may not include waveguides 106 and 108, and may guide coupled light 132 to vapor cell array 102 and probe light 142 to detector 114 of detector array 104 via optical fibers through vapor cell 112 of vapor cell array 102 via any other means (e.g., an array of light sources 130 and 140, etc.).

[0038] The detector array 104 may include a plurality of detectors 114. As described above, although Figure 1 The cross-sectional view of shows the detector array 104 as a 1D array including multiple detectors 114 in the y-direction, but the detector array 104 can be a 2D array including multiple detectors 114 in both the x-direction and the y-direction. The detectors 114 of the detector array 104 can be configured to detect electromagnetic radiation, such as infrared and / or visible light. The detectors 114 can be large bandgap solid-state visible wavelength detectors configured to operate without cooling, such as at room temperature. For example, the detector array 104 can be a charge coupled device (CCD) array, a metal oxide semiconductor-based array, such as a complementary metal oxide semiconductor (CMOS) array, or an N-type metal oxide semiconductor (NMOS) array. The detectors 114 of the detector array 104 can be configured to detect probe light from the probe light source 140. In some examples, the detector array 104 can be configured to output one or more signals proportional to the detected electromagnetic radiation, such as the detected probe light. For example, detector array 104 can be configured to output a 2D image of detected probe light, the detected probe light corresponding to detected EM radiation 152 that was transduced and / or converted into probe light 142 via vapor chamber 112. In some examples, detector array 104 can be configured to output a pixelated 2D image, e.g., an image comprising a plurality of pixels, corresponding to the detected EM radiation 152 in 2D.

[0039] Imaging optics 110 may include lenses, 1D or 2D lens arrays, diffraction gratings, stackable THz focusing optics, etc. In some examples, imaging optics are configured to direct and / or focus EM radiation 152 to be detected at vapor cell 112. In some examples, system 100 may not include imaging optics 110 and may operate as a phased array.

[0040] In some examples, system 100 can include a PIC for in-plane beam routing and detection, such as for coupled light 132 and probe light 142. For example, one or more of light source 130, light source 140, detector array 104, first waveguide 106, and second waveguide 108 can be integrated or combined as a PIC.

[0041] The computing device 120 may be configured to receive a signal from the detector array 104 indicating that the detected probe light is proportional to the EM radiation to be detected 152. The computing device 120 includes a computing engine 122, a memory 124, a communication unit 118, a processing circuit 116, one or more hardware user interfaces 128 (hereinafter referred to as "hardware user interfaces 128"), and one or more output devices 126. Figure 1In the example of , a user of computing device 120 can provide input to computing device 120 via one or more input devices (not shown) such as a keyboard, mouse, microphone, touch screen, touchpad, or other input devices coupled to computing device 120 via one or more hardware user interfaces 128.

[0042] Output device 126 may include a display, a sound card, a video graphics adapter card, speakers, a presence-sensitive screen, one or more USB ports, a video and / or audio output port, or any other type of device capable of producing tactile, audio, visual, or other output. Output device 126 may include a display device that may use technologies such as a liquid crystal display (LCD), a quantum dot display, a dot matrix display, a light-emitting diode (LED) display, an organic light-emitting diode (OLED) display, a cathode ray tube (CRT) display, electronic ink, or any other type of display that is monochrome, color, or capable of producing tactile, audio, and / or visual output as an output device.

[0043] In some examples, computing device 120 includes a communication unit 118. Communication unit 118 is configured to receive electrical signal inputs from one or more sensors, such as detector 114. Communication unit 118 can send and / or receive electrical signal inputs / outputs to coupling light source 130, probe light source 140, vapor chamber 112, and imaging optical device 110 via a wired or wireless connection. For example, computing device 120 can communicate via communication unit 118 to configure coupling light source 130, probe light source 140, vapor chamber 112, and imaging optical device 110. Communication unit 118 can be configured to convert the received electrical signal into a form that can be used by computing device 120. For example, communication unit 118 can include software or hardware configured to convert the received signal input from an analog signal to a digital signal. In another example, communication unit 118 can include software or hardware configured to compress, decompress, transcode, encrypt, or decrypt the received signal input into a form that can be used by computing device 120. In another example, the communication unit 118 may include a network interface device that receives packetized data representing image data and / or input / output data. In such an example, the intermediate device may packetize the signal to generate packetized data and send the packetized data to the computing device 120. In this manner, the communication unit 118 may be configured to interface or communicate with any of the detector 114, the probe light source 140, the vapor chamber 112, and the imaging optics 110.

[0044] The computing engine 122 can be implemented in a circuit. For example, the computing engine 122 can include a processing circuit 116, which can be any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or equivalent discrete or integrated logic circuits. The functionality of the processor described herein, including the computing engine 122 and the processing circuit 116, can be provided by the processing circuit of a hardware device, for example, supported by software and / or firmware. The computing engine 122 can be configured to generate a digital image based on the signals received from the detector array 104. The computing engine 122 can also be configured to control the output of the light sources 130 and 140 and receive information indicating the output of the light sources 130 and 140, for example, feedback content about the brightness and spectrum of the light sources 130 and 140. In some examples, the computing engine 122 can be configured to control the imaging optical device 110, for example, to change the focus and zoom.

[0045] Processing circuitry 116 can be communicatively coupled to imaging system 100, for example, via communication unit 118. For example, processing circuitry 116 can process a signal received from detector array 104 via communication unit 118, the signal being indicative of detected probe light that is proportional to detected EM radiation 152. In some examples, processing circuitry 116 can control the output of light sources 130 and 140 and receive feedback indicative of the output of light sources 130 and 140, for example, regarding the brightness and spectrum of light sources 130 and 140. In some examples, processing circuitry can communicate with imaging optics 110, for example, to change focus and zoom.

[0046] In some examples, computation engine 122 may include memory 124. Memory 124 may include any volatile or non-volatile media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, etc. Memory 124 may be a storage device or other non-transitory media. Memory 124 may be used by processing circuitry 116 to store, for example, information related to imaging system 100, such as images and image information, detector array 104 settings, light sources 130 and 140 settings, and imaging optics 110 settings. In some examples, processing circuitry 116 may store image information or data previously received from an electrical signal in memory 124 for later retrieval. In some examples, processing circuitry 116 may store determined values ​​or any other calculated values ​​in memory 124 for later retrieval.

[0047] In some examples, computing device 120 can be integrated with imaging system 100. In other examples, computing device 120 can be an external device, eg, a computing device separate from imaging system 100 and configured to communicate with imaging system 100.

[0048] Figure 2A is a perspective view of an example vapor chamber array 166 in accordance with the techniques of this disclosure. Figure 2A An isolated view of vapor chamber array 162 is illustrated as a layer of imaging system 160. In the example shown, vapor chamber array 162 includes a plurality of vapor chambers 172 arranged in a 2D array. In some examples, vapor chambers 172 may be quantum antennas, and vapor chamber array 162 may be a quantum antenna array, a phased array, an imaging array, and / or a multispectral imaging array.

[0049] Figure 2B is a perspective view of a partially transparent block diagram illustrating an example imaging system 160 according to the techniques of the present disclosure. In the example shown, the imaging system 160 includes a coupling waveguide 166, a vapor chamber array 162, and a probe waveguide 168 arranged in a layered stack with the coupling waveguide 162, wherein the coupling waveguide 162 is adjacent to the detector array 164 and the vapor chamber array 162 is between the coupling waveguide 166 and the detection waveguide 168. In some examples, the vapor chamber array 162, the coupling waveguide 166, and the probe waveguide 168 can form a PIC stack. In the example, the detector array 164 is illustrated as being separate from the other layers, but in other examples can be part of the PIC stack. According to the above Figure 1 As depicted, each of vapor cell array 162 , detector array 164 , coupling waveguide 166 , and probe waveguide 168 may be substantially similar to vapor cell array 102 , detector array 104 , first waveguide 106 , and second waveguide 108 . Figure 2B The coupled light 182 (shown as dashed lines) propagating in the y-direction within the coupling waveguide 166 is shown as a plurality of "rows" corresponding to the positions of the vapor chambers 172, and the probe light 192 (shown as a thicker solid line) propagating in the x-direction within the probe waveguide 168 is shown as a plurality of "columns" corresponding to the positions of the vapor chambers 172. In some examples, the coupled light 182 and the probe light 192 propagate in orthogonal directions within the coupling waveguide 166 and the probe waveguide 168, respectively, which can allow space for arranging the coupled light source and the probe light source along orthogonal edges of the PIC. In some examples, the coupled light 182 and the probe light 192 can propagate in any direction within the coupling waveguide 166 and the probe waveguide 168, respectively, and need not propagate in orthogonal directions.

[0050] The coupled light 182 and the probe light 192 can be substantially similar to the coupled light 132 and the probe light 142, respectively. In some examples, the probe waveguide 168 is configured to extract at least a portion of the probe light 192 to propagate through the vapor chamber 172 to the detector array 164. In some examples, the probe waveguide 168 can be a PIC including a waveguide and one or more extraction features. The coupled waveguide 166 can be configured to extract at least a portion of the probe light 182 propagating through the vapor chamber 172. In some examples, the coupled waveguide 166 can be a PIC including a waveguide and one or more extraction features.

[0051] Figures 3 to 7 Example sensors and example operating principles for detecting electromagnetic radiation in the MHz / GHz / THz frequency range are described and discussed together below.

[0052] Figure 3 is a cross-sectional view of an example sensor 200 according to the techniques of this disclosure. The sensor 200 can be a single "pixel" of the system 100 and / or the imaging system 160 described above. In the example shown, the sensor 200 includes a vapor chamber 212 disposed between a probe waveguide 246 and a coupling waveguide 248, and a photodetector 214.

[0053] In the example shown, the vapor chamber 212 includes a vapor chamber sidewall 260, a vapor chamber detector end wall 262, and a vapor chamber front end wall 264 that define a volume and are configured to hold alkali atoms within the volume. The vapor chamber 212 can include a vapor of alkali atoms 266 in the vapor and an integrated vacuum pump (not shown). The vapor chamber detector end wall 262 can be any material configured to hold alkali atoms within the volume and is substantially transparent to the coupled light 232 and the probe light 242. The vapor chamber front end wall 264 can be any material configured to hold alkali atoms within the volume and is substantially transparent to the probe light 242 and EM radiation 252 (e.g., MHz / GHz / THz EM radiation). The vapor chamber 212 can convert EM radiation 252 having megahertz (MHz), gigahertz (GHz), and terahertz (THz) ranges into optical frequencies having a picohertz (PHz) range. In terms of wavelength, vapor chamber 212 may convert electromagnetic radiation in the meter to millimeter wavelength range into electromagnetic radiation in the UV / VIS / NIR wavelength range.

[0054] The coupling waveguide 236 can be disposed on a substrate 234. The substrate 234 can be any material suitable for providing mechanical support for the coupling waveguide 236 to support the generally planar shape of the coupling waveguide 236 and can be substantially transparent to the coupled light 232. In some examples, the substrate 234 can have a lower refractive index than the coupling waveguide 236 at the frequency of the coupled light 232, e.g., to enable TIR within the coupling waveguide 236. In some examples, the sensor 200 can exclude the substrate 234, and the coupling waveguide 236 can be made of a suitable material and a suitable thickness to maintain a generally planar shape.

[0055] The coupling waveguide 236 may include a coupling light indicator 238. In some examples, the coupling waveguide 236 may be a PIC including a waveguide and one or more extraction features. The coupling light indicator 238 may be configured to extract the coupling light 232 from the coupling waveguide 236 and direct the coupling light 232 to the vapor of alkali atoms 266 within the volume of the vapor chamber 212. For example, the coupling light indicator 238 may include one or more extraction features, such as a surface relief pattern on any surface of the coupling waveguide 236 where TIR occurs, and the surface relief pattern may be a diffraction grating. In other examples, the coupling light indicator 238 may include a distribution of painted dots on any surface of the coupling waveguide 236 where TIR occurs, a change in shape (e.g., a taper, a curve, a discontinuity) of any surface of the coupling waveguide 236 where TIR occurs, a scattering material and / or structure within the bulk material of the coupling waveguide 236 at the location of the coupling light indicator 238, and the like.

[0056] The coupling waveguide 236 can be arranged along any one of the vapor chamber sidewall 260, the vapor chamber detector end wall 262, or the vapor chamber front end wall 264, and is configured to extract the coupled light 232 into the vapor chamber 212 to the vapor of alkali atoms 266. In other words, the coupled light 232 can enter the vapor chamber 212 from any direction. In the example shown, the coupling waveguide 236 is arranged along the vapor chamber detector end wall 262 between the photodetector 214 and the vapor chamber 212, and generally has a minimum dimension, such as thickness, perpendicular to the photodetector 214 and confines the coupled light 232 to propagate within its thickness and in the xy direction via TIR. In other examples, the coupling waveguide 236 can be set along the vapor chamber front end wall 264, for example, on the other side of the vapor chamber 212 and the same side of the vapor chamber 212 as the detection waveguide 246. In other examples, the sensor 200 may include a plurality of coupled waveguides 236 disposed between one or more vapor chambers 212, for example, generally with a plane having its smallest dimension in the x or y direction (e.g., perpendicular to the waveguides 236, such as Figure 3 as shown), and confines the coupled light 232 to propagate within its thickness and in the yz or xz direction.

[0057] The coupling waveguide 236 can be made of any suitable material that is substantially transparent to the coupled light 232, such as UV / VIS / NIR light. For example, the coupling waveguide 236 can be glass, a polymer material, polycarbonate, polymethyl methacrylate (PMMA), or the like.

[0058] In the example shown, the coupling waveguide 236 can be an “edge-illuminated” waveguide, e.g., the coupled light 232 can be introduced into the coupling waveguide 236 from any edge of the coupling waveguide 236, e.g., any surface of the coupling waveguide 236 including the smallest dimension of the coupling waveguide 236. In the example shown, the coupled light 232 can enter the coupling waveguide 236 via the edge 270 and can propagate along the waveguide 236 in the y-direction via TIR and can be extracted and directed by the coupled-light indicator 238 toward the vapor of the alkali atoms 266.

[0059] The probe waveguide 246 can be disposed on a substrate 244. The substrate 244 can be any material suitable for providing mechanical support for the probe waveguide 246 to support the generally planar shape of the probe waveguide 246 and can be substantially transparent to the probe light 242. In some examples, the substrate 244 can have a lower refractive index than the probe waveguide 246 at the frequency of the probe light 242, for example, to enable TIR within the probe waveguide 246. In some examples, the sensor 200 can exclude the substrate 244, and the probe waveguide 246 can be made of a suitable material and a suitable thickness to maintain a generally planar shape. In some examples, the substrate 244 can be substantially similar to the substrate 234.

[0060] The detection waveguide 246 may include a probe light indicator 248. In some examples, the probe waveguide 246 may be a PIC including a waveguide and one or more extraction features. The probe light indicator 248 may be configured to extract the probe light 242 from the probe waveguide 246 and guide the probe light 242 to the photodetector 214 through the vapor of alkali atoms 266 within the volume of the vapor chamber 212. For example, the probe light indicator 248 may include one or more extraction features, such as a surface relief pattern on any surface of the probe waveguide 246 where TIR occurs, and the surface relief pattern may be a diffraction grating. In other examples, the probe light indicator 248 may include a distribution of painted dots on any surface of the probe waveguide 246 where TIR occurs, a shape change (e.g., a taper, a curve, a discontinuity) on any surface of the probe waveguide 246 where TIR occurs, a scattering material and / or structure within the bulk material of the probe waveguide 246 at the location of the probe light indicator 248, and the like.

[0061] The probe waveguide 246 can be configured to extract the probe light 242 through the vapor chamber 212 to the photodetector 214. In some examples, the vapor chamber 212 can act like an optical shutter for the probe light 242, which can change the amount of the probe light 242 transmitted through the vapor chamber 212 due to a change in the EIT of the vapor of the alkali atoms 266 within the vapor chamber 212 corresponding to the amount and / or frequency of the incident EM radiation 252. For example, a change in the EIT of the vapor of the alkali atoms 266 with respect to the probe light 242 can be caused by the EM radiation 252 incident on the vapor of the alkali atoms 266, and the amount of the probe light 242 detected by the photodetector 214 can be proportional to the amount and / or frequency content of the EM radiation 252. In this way, the vapor chamber 212 can be used as a transducer of the amount and / or frequency content of the EM radiation 252 by transducing the response of the amount and / or frequency content of the EM radiation 252 incident on the vapor chamber 212 (i.e., the EIT of the vapor of the alkali atoms 266 to the probe light 242) into a detected amount of probe light 242.

[0062] Generally speaking, the probe light 242 can propagate through the vapor of the alkali atoms 266 to the photodetector 214. In the example shown, the probe waveguide 246 is disposed along the vapor chamber end wall 262 opposite the photodetector 214, is generally a plane having a smallest dimension (e.g., thickness), is perpendicular to the photodetector 214, and confines the coupled light 242 to propagate within its thickness and in the xy direction via TIR. In some examples, the probe waveguide 246 can be disposed along any of the vapor chamber sidewalls 260, the vapor chamber end wall 262, or the vapor chamber front wall 264 in any direction and is configured to extract the probe light 242 through the vapor chamber 212 to the photodetector 214. For example, the probe waveguide 246 can be disposed along the vapor chamber front end wall 264, e.g., on the other side of the vapor chamber 212 and on the same side of the vapor chamber 212 as the coupling waveguide 236, to extract the probe light 246 into the vapor chamber 212 and through the vapor of the alkali atoms 266, and a reflector (not shown) can reflect the probe light 242 through the vapor of the alkali atoms 266 back to the photodetector 214. In other examples, the reflector can be arranged to reflect the probe light 242 to the photodetector 214 after propagating through at least a portion of the vapor of the alkali atoms 266. For example, the sensor 200 may include a plurality of probe waveguides 246 disposed between one or more vapor chambers 212, e.g., generally with their smallest dimension in the x or y direction (e.g., perpendicular to the waveguide 236, as shown). Figure 3266 ) and confines the probe light 242 to propagate within its thickness and in the yz or xz direction. One or more probe light indicators 248 can extract and guide the probe light 242 to the vapor of alkali atoms 266 through one or both sides of the vapor chamber sidewall 260, which can be substantially transparent to the probe light 242. A reflector (not shown) can be arranged to reflect the probe light 242 entering the vapor chamber 212 toward the photodetector 214 via the sidewall 260 after propagating through at least a portion of the volume of the vapor containing the alkali atoms 266. Typically, the coupling waveguide 236 and the probe waveguide 246 can be arranged along, around, near, in contact with, or separately from any one of the vapor chamber sidewall 260, the vapor chamber end wall 262, and the vapor chamber front end wall, and are configured to extract the coupled light 232 and the probe light 242, respectively, into the vapor chamber 212. In some examples, the probe waveguide can be configured to guide the probe light 242 into the vapor chamber 212 and such that the probe light 242 guided into the vapor chamber 212 is subsequently directed toward the detector 214 , for example, with or without subsequent light guides such as one or more mirrors, lenses, or gratings.

[0063] The detection waveguide 246 can be made of any suitable material that is substantially transparent to the probe light 242, such as UV / VIS / NIR light. For example, the probe waveguide 246 can be glass, a polymer material, polycarbonate, polymethyl methacrylate (PMMA), etc. In some examples, the probe waveguide 246 can be substantially similar to the coupling waveguide 236 and can include one or more probe light indicators 248 that are substantially similar to the coupling light indicators 238.

[0064] In the example shown, the probe waveguide 246 can be an “edge-illuminated” waveguide, e.g., the probe light 242 can be injected into the probe waveguide 246 from any edge of the probe waveguide 246, e.g., any surface of the probe waveguide 246 that includes the smallest dimension of the probe waveguide 246. In the example shown, the probe light 242 can enter the probe waveguide 246 via the edge 280 and can propagate along the probe waveguide 246 in the y-direction via TIR and can be extracted and directed toward the vapor of the alkali atoms 266 by the probe light pointer 248.

[0065] The photodetector 214 can be configured to detect electromagnetic radiation, such as infrared and / or visible light. The photodetector 214 can be substantially similar to the detector 114 described above, and can be one of an array of photodetectors 214, for example, a pixel detector in a 2D focal plane array of pixels. The photodetector 214 can be a large bandgap solid-state visible wavelength detector configured to operate without cooling, for example at room temperature. For example, the detector array 214 can be pixels of a charge coupled device (CCD) array, a metal oxide semiconductor-based array, such as a complementary metal oxide semiconductor (CMOS) array, or an N-type metal oxide semiconductor (NMOS) array. The photodetector 214 can be configured to detect the probe light 242, and can be configured to output one or more signals proportional to the detected probe light 242.

[0066] Figure 4 is a cross-sectional view of an example sensor 300 according to the techniques of this disclosure. The sensor 300 may be a single "pixel" of the system 100 and / or imaging system 160 described above. The sensor 300 may be similar to the one described above with respect to Figure 3 The sensor 200 shown and described is substantially the same, except that the coupling waveguide and the probe waveguide can form the vapor chamber end wall and the vapor chamber front wall, respectively, e.g., the vapor chamber can be integrated with the coupling and probe waveguides. The sensor 300 can also include differences in the support for the vapor chamber and the integration of the coupling and probe waveguides, e.g., the coupling and probe waveguide materials are adapted for the vapor chamber walls. In the illustrated example, the sensor 300 includes a vapor chamber 312 disposed between a probe waveguide 346 and a coupling waveguide 348, and a photodetector 214.

[0067] In the example shown, the vapor chamber 312 includes a vapor chamber sidewall 360, a coupling waveguide 336, and a probe waveguide 346 that define a volume and are configured to keep alkali atoms within the volume. The vapor chamber 312 can be substantially the same as the vapor chamber 212, with the difference that the coupling waveguide 336 and the probe waveguide 346 can be the vapor chamber end wall and the front end wall, respectively, and the vapor chamber sidewall 360 can extend completely between the coupling waveguide 336 and the probe waveguide 346 to define the volume of the vapor chamber 312. The vapor chamber 312 can include the vapor of the alkali atoms 266 and an integrated vacuum pump (not shown) within the volume.

[0068] The coupling waveguide 336 can be configured to accommodate the vapor of the alkali atoms 266. For example, the coupling waveguide 336 can be made of a material suitable for accommodating the alkali atoms 266, still transparent to the coupling light 232 and the probe light 244, and having a refractive index relative to the vapor of the alkali atoms 266 to enable TIR at the interface between the coupling waveguide 236 and the vapor of the alkali atoms 266, such as glass or any other suitable material. In addition, the coupling waveguide 336 and its arrangement relative to the other components of the sensor 300 can be the same as described above with respect to Figure 3 The coupled waveguides 236 shown and described are generally similar.

[0069] The coupling waveguide 336 can include one or more coupling light guides 338 configured to extract the coupled light 232 and guide the coupled light 232 into the vapor of the alkali atoms 266. In some examples, the coupling waveguide 336 can be a PIC including a waveguide and one or more extraction features. The coupling light extractor 338 can be substantially similar to the coupling light guide 238 shown and described above, except that the coupling light guide 338 can be configured to extract the coupled light 232 into the vapor of the alkali atoms 266, which can have a different refractive index than air and / or vacuum.

[0070] The probe waveguide 346 can be configured to retain the vapor of the alkali atoms 266. For example, the probe waveguide 346 can be made of a material suitable for protecting the alkali atoms 266, yet transparent to the probe light 244 and the EM radiation 252, and having a refractive index relative to the vapor of the alkali atoms 266 to enable TIR at the interface between the probe waveguide 246 and the vapor of the alkali atoms 266, such as glass or any other suitable material. Furthermore, the probe waveguide 346 and its arrangement relative to the other components of the sensor 300 can be the same as described above with respect to Figure 3 The probe waveguide 246 shown and described is generally similar.

[0071] The probe waveguide 346 can include one or more probe light indicators 348 configured to extract the probe light 242 and direct the probe light 242 into the vapor of the alkali atoms 266. In some examples, the probe waveguide 346 can be a PIC including a waveguide and one or more extraction features. The probe light extractor 348 can be substantially similar to the probe light guide 248 shown and described above, except that the probe light guide 348 can be configured to extract the probe light 242 into the vapor of the alkali atoms 266, which can have a different refractive index than air and / or vacuum.

[0072] Figure 5 is a flow chart of an example method 500 for imaging EM radiation according to the techniques of this disclosure. Figures 3 and 4 The sensors 200 and 300 shown and described are described below with reference to Figure 6 and Figure 8 The energy level diagrams 600 and 800 shown and described, and the following references Figure 7 Graph 700 is shown and described.

[0073] The coupled light and the probe light can be injected into the coupling waveguide and the probe waveguide of the sensor, respectively (502). For example, the coupled light 232 can be injected into the coupling waveguide 236 and / or 336 via the edge 270, and the probe light 242 can be injected into the probe waveguide 246 and / or 346 via the edge 280. The coupled light 232 can propagate within the coupling waveguide 236 and / or 336 and can be extracted from the coupling waveguide 236 and / or 336 via one or more extraction features (such as the coupling light guide 238 and / or 348). In some examples, the coupled light 232 can be extracted at multiple locations via multiple coupling light guides 238 and / or 338. Similarly, the probe light 242 can propagate within the probe light waveguide 246 and / or 346 and can be extracted from the probe waveguide 246 or 346 via one or more extraction features (such as the probe light guide 238 and / or 348). The probe light 242 can be extracted at multiple locations via multiple probe light guides 248 and / or 348. For example, the sensor 200 and / or 300 can correspond to each "pixel" of the 2D array imaging system 100 or 160, and each coupling light guide 238 and / or 338 can correspond to the vapor cell 112 and / or 172 and detector 114 of the imaging system 100 and / or 160. For each pixel of the array, the coupled light 232 can be extracted from the coupling waveguide 236 and / or 336, and the probe light 242 can be extracted from the probe waveguide 246 and / or 346.

[0074] The probe light 242 can excite the alkali atoms in one or more vapor chambers 112 from a first quantum state to a second quantum state, for example, from a ground state to a first excited state (504). For example, the probe light 242 can be extracted from the probe waveguide 246 and / or 346 and guided toward the one or more photodetectors 214 through the one or more vapor chambers 112, 212 and / or 312, and can excite the alkali atoms in the one or more vapor chambers 112, 212 and / or 312 from the first quantum state to the second quantum state. In some examples, the photons of the probe light 242 can be absorbed by alkali atoms, such as rubidium atoms, cesium atoms, etc., in the one or more vapor chambers 112, 212 and / or 312. The energy absorbed by the alkali atoms can drive the electrons in the alkali atoms into an excited state, for example, an intermediate quantum state. The quantum state transition of the rubidium atom is as follows Figure 6 shown. Figure 6 is an illustration of an example energy diagram 600 for an alkali atom including at least one Rydberg state in accordance with the presently disclosed techniques. Figure 6In the example shown, the probe light 242 can be a laser with a wavelength of 780 nanometers (nm), which can drive the rubidium atoms from |5S 1 / 2 >Quantum state (e.g. ground state) to |5P 3 / 2 >Transitions of quantum states (e.g., intermediate states).

[0075] The coupling light 232 can excite the alkali atoms in one or more vapor chambers 112 from the second quantum state to the third quantum state, for example, from the first excited state to the Rydberg state (506). For example, the coupling light 232 extracted from the coupling waveguide 246 and / or 346 and guided toward the one or more vapor chambers 112, 212 and / or 212 can excite the alkali atoms in the one or more vapor chambers 112, 212 and / or 312 from the second quantum state to a Rydberg state with a higher principal quantum number n, such as the third quantum state. In some examples, the photons of the coupling light 232 can be absorbed by the alkali atoms in the second quantum state excited by the probe light 242, such as rubidium atoms, cesium atoms, etc. The energy of the coupling light 232 absorbed by the alkali atoms can drive the electrons of the alkali atoms into another excited state, such as the Rydberg quantum state. In Figure 6 In the example shown, the coupling light 232 can be a 480 nm wavelength laser, which can drive the rubidium atoms from the 5P 1 / 2 The quantum state transitions to a Rydberg state |a>. As described above, alkali atoms in the Rydberg state can have loosely bound valence electrons that can be perturbed or ionized by collisions or external fields (e.g., MHz / GHz / THz radiation). Alkali atoms in the Rydberg state |a> can exhibit electromagnetically induced transparency (EIT) for frequencies close to those of the probe light 242. In the example shown, EM radiation 252 incident on the vapor of alkali atoms 266 in the Rydberg state |a> can resonate with the energy splitting between the Rydberg state |a> and the Rydberg state |b> and can induce EIT in the vapor of alkali atoms 266, e.g., the probe light 242 propagating through the Autler-Townes splitting of an absorption line of the vapor of alkali atoms 266.

[0076] In some examples, each alkali atom of the vapor of alkali atoms 266 in any one of the one or more vapor cells 112, 212, and / or 312 can respond like an independent transducer, e.g., by converting incident resonant EM radiation 252 into an optical signal response via probe light 242. The alkali atom clusters of the vapor of alkali atoms 266 in any one of the one or more vapor cells 112, 212, and / or 312 can incoherently amplify the signal.

[0077] In some examples, alkali atoms can be laser cooled, for example, to reduce the motion of the alkali atoms in the vapor. In some examples, laser cooling of the alkali atoms can increase the stability of the atoms in any intermediate quantum states above the Rydberg state and / or the ground state.

[0078] One or more photodetectors 214 may detect the amount of probe light after it propagates through one or more vapor cells, for example, probe light 242 (508) after propagating through one or more vapor cells 112, 212, and / or 312. In some examples, alkali atoms may be detected as probe light 242 at |5S 1 / 2 >→|5P 3 / 2 >Absorption spectrum of the detuning function on resonance. In the absence of the coupled light 232, the absorption spectrum of the probe light 242, after passing through one or more vapor chambers 112, 212 and / or 312, looks like a wide (near GHz), room-temperature Doppler-broadened dip in the intensity level of the probe light 242. In the presence of the strongly resonant coupled light 232, the refractive index of the vapor of the alkali atoms 266 is altered around the resonant frequency of the probe light 242 so that a narrow transparent "window" of the spectrum is "opened". In some examples, the EIT spectral "window" is several megahertz wide, with the probe light 242 exhibiting a narrow peak in intensity at the bottom of the Doppler distribution. The peak can represent the resonant condition of the probe light 242 and the coupled light 232, and the presence of the peak can indicate that the vapor of the alkali atoms 266 can couple well to the Rydberg state. In some examples, the energy level of the state (e.g., Figure 6 The Ω shown RF For example, the signal response of the probe light 242 detected by the photodetector 214 may vary in proportion to the perturbation of the energy levels of the Rydberg states due to the EM radiation 252 incident on the vapor cells 212 and / or 312, as described below with reference to Figure 7 The spectral narrowness of the EIT peak allows for sub-Doppler precision measurement of the atomic response to EM radiation 252 in a room temperature vapor cell.

[0079] Figure 7 7 is an example graph 700 illustrating an absorption signal response of the probe light 242 as a function of the probe light frequency detuning, according to the techniques of this disclosure. In the example, the absorption signal response example corresponds to the amount of probe light 242 detected by the one or more photodetectors 214 as a function of detuning (e.g., frequency sweeping and / or glancing) the probe light 242. In the example shown, a frequency of 0 Hz on the x-axis of the graph 700 corresponds to |5S 1 / 2 >→|5P 3 / 2>resonance frequency, for example, approximately 780 nm (e.g., 780.2460209 nm or 384.228022 THz). For reference, plot 700 corresponds to a wavelength range of approximately ±0.0001625 nm from a detuning range of ±80 MHz. Plot 700 includes four probe light 242 signal response plots corresponding to four different amounts of 17.04 GHz radio frequency (RF) EM radiation 252 incident on the vapor of alkali atoms 266. Plot 702 is the probe light 242 absorption signal response to 0 milliwatts (mW) of 17.04 GHz RF light (e.g., EM radiation 252) incident on the vapor chamber 212 and / or 312, and is a Doppler broadened decrease in the intensity level of the probe light 242 after propagation through the vapor chamber 212 and / or 312. Graph 708 shows the absorption signal response of probe light 242 to 1.0 mW of 17.04 GHz RF light incident on vapor chamber 212 and / or 312, and includes a narrow peak in the intensity of probe light 242 at the bottom of the Doppler distribution, such as the EIT window. Graphs 704 and 706 show the absorption signal response of probe light 242 to 0.2 mW and 0.5 mW of 17.04 GHz RF light, respectively, and illustrate the relative changes in the amplitude and shape of the absorption signal response when different amounts of 17.04 GHz RF light are incident on vapor chamber 212 and / or 312.

[0080] Processing circuitry, such as processing circuitry 116, may determine the amount and / or one or more frequencies of EM radiation (e.g., EM radiation 252) based on the amount of probe light detected by one or more photodetectors 214 (510). For example, processing circuitry may determine the amount and / or one or more frequencies of EM radiation 252 incident on vapor chamber 212 and / or 312 based on the absorption signal response of probe light 242. In some examples, processing circuitry 116 may determine the amount and / or one or more frequencies of EM radiation 252 incident on vapor chamber 212 and / or 312 based on any amplitude, shape, and spectral content of the absorption signal response of probe light 242 after propagation through vapor chamber 212 and / or 312 as a function of detuning, wavelength sweeping and / or sweeping, and / or frequency sweeping and / or sweeping. In other words, for example, the absorption signal response plots may be similar to the absorption signal response plots 702 through 708 described above.

[0081] Processing circuitry, such as processing circuitry 116, may form an image (512) based on the determined amount of EM radiation (e.g., EM radiation 252) received at the plurality of detectors. For example, the processing circuitry may determine a grayscale and / or color representation of each "pixel" of imaging system 100 and / or 160 and / or plurality of sensors 200 and / or 300.

[0082] In some examples, imaging systems 100 and / or 160 and sensors 200 and / or 300 can be configured to excite alkali atoms in a vapor cell (e.g., vapor cells 112, 212, and / or 312) using multiple frequencies of coupled light 232 and / or probe light 242. For example, Figure 6 The illustrated example illustrates a "three-level" system, in which alkali atoms can be excited from a first energy level to a second energy level, e.g., an intermediate energy level, via probe light 242, and from the second energy level to a third energy level in which the alkali atoms are in a Rydberg state. In some examples, any one of the imaging systems 100 and / or 160 and sensors 200 and / or 300 can be configured to excite the alkali atoms in the vapor cell using a system comprising more or fewer energy levels. For example, any one of the imaging systems 100 and / or 160 and sensors 200 and / or 300 can be configured to excite the alkali atoms in the vapor cell using a two-level system or any other digital system. In some examples, probe light sufficient to directly excite the alkali atoms from a first state, e.g., a ground state, to a Rydberg state may require probe light 242 having a frequency corresponding to far-ultraviolet light, which can make implementing a two-level system difficult and / or expensive using current light sources and detectors. In contrast, a system with three or more levels can have lower difficulty and implementation costs because higher performance and lower-cost light sources and detectors can be obtained.

[0083] Figure 8 is an illustration of an example energy diagram 800 for an alkali atom including at least one Rydberg state in accordance with the presently disclosed techniques. Figure 8 In the example shown, the probe light 242 can be a laser with a wavelength of 780 nanometers (nm), which can drive the rubidium atoms from |5S 1 / 2 >Quantum state (e.g. ground state) to |5P 3 / 2 >Transition of quantum states (e.g., intermediate states). Light 842 can be a laser with a wavelength of 776 nanometers (nm), which can drive the rubidium atoms from the intermediate |5P 3 / 2 > quantum state to another intermediate |c> quantum state. Coupling light 832 can be a 1260 nm wavelength laser, which can drive the transition of the rubidium atoms from the |c> quantum state to the Rydberg state |a>. In some examples, 1260 nm laser sources can be more common, less expensive, and more powerful than blue 480 nm laser sources.

[0084] The coupled light 832 may be delivered to the vapor chamber 112, 212, and / or 312 via one of the coupling waveguides 236 and / or 336, and the light 842 may be delivered to the vapor chamber 112, 212, and / or 312 via one of the probe waveguides 246 and / or 346. For example, the coupling waveguides 236 and / or 336 and the probe waveguides 236 and / or 336 may be configured to simultaneously receive and distribute a plurality of optical frequencies, such as any one of the coupled light 232 and 832, the light 842, and the probe light 242, and may be configured to extract and direct one or more of the plurality of frequencies to the vapor chamber, such as the vapor chamber 112, 212, and / or 312.

[0085] In some examples, any of the sensors 200, 300, 1100, and / or 1200 can be configured to excite, for example, alkali atoms in any of the vapor chambers 112, 212, 312, 1112, or 1212 via multiple quantum states and / or energy levels. For example, the waveguide 236 or 246 (e.g., the PIC 236 and 246) can be configured to guide two or more wavelengths of light into any of the vapor chambers 112, 212, 312, 1112, and 1212 and incident on the vapor of the alkali atoms, and each of the two or more wavelengths of light can be configured to excite the alkali atoms from a low excited state to a higher excited state in sequence from a first excited state to a Rydberg state. In some examples, by using the (high wavelength) low frequency excitation light as described above, the alkali atoms are excited from a low state via one or more intermediate states to a Rydberg state, for example, a "three or more photon" excitation scheme can be compared to a "two-photon" excitation scheme (as described in reference). Figure 6 ) reduces the photoelectric effect of the incident light device on the alkali atoms. For example, since the alkali atoms are excited to a high state using low-energy excitation light (e.g., low-frequency light), the alkali atoms are excited via multiple quantum states and / or energy levels, and since the photoelectric effect is reduced relative to the two-photon scheme, the background charge in the vapor can be reduced relative to the two-photon scheme. In other words, the net effect of several lower energy level transitions to excite the alkali atoms to Rydberg states is a reduction in the background charge that may accumulate in the vapor chamber due to the photoelectric effect compared to the net effect of two higher energy level transitions. In some examples, the reduction in background charge may reduce the amount of background charge that may accumulate in the vapor chamber due to the incident EM radiation 252 (as described below with reference to Figures 10 and 11 The noise in the measurement of the ionization of excited alkali atoms in Rydberg states (shown and described above) is reduced, thereby improving the readout sensitivity of sensors 1100 and 1200 described below. For example, the amount of current flowing in circuit 1120 and / or 1220 can correspond to the ionization of the excited alkali atoms (signal) and any background charge (noise) in the vapor of alkali atoms.

[0086] Figure 9 is a block diagram of an example system 900 for sensing EM radiation in accordance with the techniques of this disclosure. Figure 9The system 900 includes a probe laser 942, a coupling laser 932, a vapor cell 912, EM radiation 952, a detector 914, a lock-in amplifier 902, a function generator 904, and an acousto-optic modulator 906. In some examples, the lock-in amplifier 902, the function generator 904, and the acousto-optic modulator 906 can be configured in a feedback loop to tune the coupling laser 932 to the resonant frequency of the alkali atoms in the vapor cell 912. The system 900 can be used to excite the vapor of the alkali atoms in the vapor cell 912 to a Rydberg state and determine the amount and / or frequency 952 of EM radiation in the MHz / GHz / THz frequency range based on the EIT of the alkali atom vapor to the probe light of the probe laser 942 and / or the perturbation of the EIT of the probe light from the probe laser 942.

[0087] Figure 10 is a cross-sectional view of an example sensor 1100 according to the techniques of this disclosure. Sensor 1100 may be a single "pixel" of system 100 and / or imaging system 160 described above. Sensor 1100 may be similar to the one described above with respect to Figure 3 The sensor 300 shown and described is substantially the same except that the photodetector 214 is removed and circuitry 1120 is included. In the example shown, the sensor 1100 includes a vapor chamber 1112 disposed between a probe waveguide 346 and a coupling waveguide 348, and circuitry 1120.

[0088] In the example shown, the circuit 1120 includes a first electrode 1102, a second electrode 1104, an electrical power source 1106, and an ammeter 1108. The first electrode 1102 and the second electrode 1104 extend within the vapor chamber 1112 and can form part of a wall of the vapor chamber 1112. In the example shown, the first electrode 1102 and the second electrode 1104 are disposed on the coupling waveguide 336 and the probe waveguide 346, respectively. The first electrode can be connected to a first terminal of the electrical power source 1106, such as a negative terminal or a ground terminal. The ammeter 1108 can be connected to a second terminal, such as a positive terminal of the power source 1106 and the second electrode 1104, and can be configured to measure a current flowing in the circuit 1120. The power source 1106 can be configured to apply a voltage across the first electrode 1102 and the second electrode 1104. In some examples, the power supply 1106 and the first and second electrodes 1102 and 1104 can be configured to apply 100 volts between the first and second electrodes 1102 and 1104 with a 5 mm separation.

[0089] In operation, the amount of current flowing in circuit 1120 corresponds to the ionization of alkali atoms within vapor chamber 1112. In some examples, the Rydberg-state alkali atoms within vapor chamber 1112 may be sensitive to EM radiation 252, i.e., the ionization of the alkali atoms corresponds to changes in the frequency and / or amount of EM radiation 252, and may change in response to changes in EM radiation 252, which in turn may result in changes in the amount of current flowing in circuit 1120. Amperemeter 1108 may then determine the amount of current flowing, and amperemeter 1108 and / or circuit 1112 may be configured to output a signal related to the change in the current in circuit 1112.

[0090] Figure 11 is a cross-sectional view of an example sensor 1200 according to the techniques of this disclosure. The sensor 1200 may be a single "pixel" of the system 100 and / or imaging system 160 described above. The sensor 1200 may be similar to the one described above with respect to Figure 10 The sensor 1100 shown and described is substantially the same except that the coupling waveguide 336 and the probe waveguide 346 are removed. In the example shown, the coupled light 232 and the probe light 242 can be guided to be incident on the alkali atoms of the vapor cell 1212, for example, via a light guiding device (not shown).

[0091] In the example shown, circuit 1220 can be connected to Figure 10 Circuit 1120 is substantially similar to that of FIG. 1 , except that first electrode 1102 and second electrode 1104 may be at least partially disposed on the inner surfaces of substrates 234 and 244, rather than waveguides 336 and 346, which are not included in sensor 1200. In the example shown, first electrode 1102 and second electrode 1104 extend within vapor chamber 1212 and may form part of a wall of vapor chamber 1212. Figure 10 Similar to circuit 1120 in vapor chamber 1212, the amount of current flowing in circuit 1220 corresponds to the ionization of the alkali atoms within vapor chamber 1212. In some examples, the Rydberg-state alkali atoms within vapor chamber 1212 may be sensitive to EM radiation 252, i.e., the ionization of the alkali atoms may vary corresponding to the frequency and / or amount of EM radiation 252 and may vary in response to the variation in EM radiation 252, which in turn may result in a variation in the amount of current flowing in circuit 1220. Amperemeter 1108 may then determine the amount of current flowing, and amperemeter 1108 and / or circuit 1212 may be configured to output a signal related to the variation in the current in circuit 1212.

[0092] Figure 12 is a flow chart of an example method 1300 for imaging electromagnetic radiation according to the techniques of this disclosure. Figures 10 and 11 The sensors 1100 and 1200 shown and described are described below with reference to Figure 6 and Figure 8 The energy level diagrams 600 and 800 shown and described, and the following references Figure 7 Graph 700 is shown and described.

[0093] As mentioned above, reference Figure 5 and steps 502, 504, and 506, the coupled light and the probe light may be injected into the coupled waveguide and the probe waveguide (1302), respectively, of the sensor, such as, for example, sensor 1100, the probe light 242 may be guided toward one or more vapor chambers 1112 and / or 1212, and may excite the alkali atoms in the one or more vapor chambers 1112 and / or 1212 from the first quantum state to the second quantum state (1304), and the coupled light 232 may be guided toward one or more vapor chambers 1112 and / or 1212, and may excite the alkali atoms in the one or more vapor chambers 1112 and / or 1212 from the second quantum state to a Rydberg state having a high principal quantum number n, such as a third quantum state (1306).

[0094] The circuit may apply a voltage (1308) across two electrodes within one or more vapor chambers 1112 and / or 1212. For example, a first electrode and a second electrode may be spaced apart within vapor chambers 1112 and / or 1212 and may be connected to a power source configured to apply a voltage across the electrodes.

[0095] The ammeter can determine and / or detect a current flowing through a circuit including the first electrode and the second electrode and can be correlated to ionization of alkali atoms in one or more vapor cells (1310). For example, EM radiation 252 incident on alkali atoms within vapor cells 1112 and / or 1212 can ionize the alkali atoms within vapor cells 1112 and / or 1212. The ionization of the alkali atoms within vapor cells 1112 and / or 1212 can be related to the frequency and / or amount of the incident EM radiation 252. The ammeter 1108 can detect a corresponding amount of current, and changes in the frequency and / or amount of EM radiation 252 can cause corresponding changes in the amount of current detected by the ammeter 1108.

[0096] Various examples have been described. These and other examples are within the scope of the appended claims. For the purposes of this disclosure, the operations shown in the figures need not be performed in the manner suggested by the illustrations and may be performed in any order unless otherwise specified. Furthermore, the term "substantially" is used to describe, to a great or significant extent, or in most cases, given its standard definition; essentially.

[0097] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the technology may be implemented within one or more microprocessors, DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logic QRS circuits, as well as any combination of these components, which are embodied in external devices such as physician or patient programmers, stimulators, or other devices. The terms "processor" and "processing circuitry" may generally refer to any of the foregoing logic circuits, alone or in combination with other logic circuits or any other equivalent circuits, and alone or in combination with other digital or analog circuits.

[0098] For aspects implemented in software, at least some of the functionality attributed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium in the form of RAM, DRAM, SRAM, magnetic disk, optical disk, flash memory, or EPROM or EEPROM. The instructions may be executed to support one or more aspects of the functionality described in this disclosure.

[0099] Furthermore, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules. Describing different features as modules or units is intended to highlight different functional aspects and does not necessarily imply that these modules or units must be implemented by separate hardware or software components. Rather, the functionality associated with one or more modules or units may be performed by separate hardware or software components or integrated within common or separate hardware or software components. Furthermore, these techniques may be fully implemented in one or more circuits or logic elements.

Claims

1. A sensor comprising: a vapor chamber comprising vapor of alkali atoms; a first photonic integrated circuit PIC forming a wall of the vapor chamber, wherein the first photonic integrated circuit PIC comprises extraction features configured to direct light of a first wavelength into the vapor chamber and incident on the vapor of the alkali atoms, wherein the light of the first wavelength is configured to excite the alkali atoms from a ground state to a first excited state; and A detector is configured to detect a response of the alkali atom to incident electromagnetic radiation after the alkali atom is excited from the first excited state to a Rydberg state.

2. The sensor according to claim 1, wherein The first PIC includes: A first waveguide is configured to guide light at the first wavelength, wherein the first waveguide includes the extraction feature.

3. The sensor according to claim 2, further comprising: a second PIC configured to direct light of a second wavelength into the vapor cell and incident on the vapor of the alkali atoms, wherein the light of the second wavelength is configured to excite the alkali atoms from the first excited state to the Rydberg state, wherein the second PIC comprises: a second waveguide configured to guide light of the second wavelength; and An extraction feature is configured to direct light at the second wavelength from the second waveguide into the vapor chamber and incident on the vapor of alkali atoms.

4. The sensor according to claim 3, wherein The first PIC is disposed along a first side of the steam chamber, and wherein the second PIC is disposed along a second side of the steam chamber.

5. The sensor according to claim 3, wherein The first PIC is on a first side of the vapor chamber, and wherein the second PIC is on a second side of the vapor chamber, wherein the first side is different from the second side.

6. The sensor according to claim 3, wherein At least one of the first PIC and the second PIC is configured to direct light of two or more wavelengths into the vapor chamber and incident on the vapor of the alkali atoms, wherein each of the two or more wavelengths of light is configured to excite the alkali atoms from a lower excited state to a higher excited state sequentially from the first excited state to the Rydberg state.

7. The sensor according to any one of claims 1 to 6, wherein: The detector comprises a photodetector, wherein the response of the alkali atoms in the Rydberg state to the incident electromagnetic radiation comprises a change in electromagnetically induced transparency (EIT) of the alkali atoms to light of the first wavelength.

8. The sensor according to claim 7, wherein The photodetector is configured to detect an amount of light at the first wavelength after the light at the first wavelength propagates through the vapor cell, wherein the photodetector is configured to output a signal proportional to the amount of light at the first wavelength detected.

9. The sensor according to any one of claims 1 to 6, wherein: The detector comprises: an electrical circuit comprising at least two electrodes spaced apart within the vapor chamber and configured to apply a voltage across the at least two electrodes; and an ammeter configured to measure a current of the circuit comprising the at least two electrodes, wherein the response of the alkali atoms in the Rydberg state to the incident electromagnetic radiation comprises a change in the ionization of the vapor of the alkali atoms.

10. The sensor according to claim 9, wherein The ammeter is configured to output a signal related to a change in the current of the circuit in response to a change in the ionization of the vapor of the alkali atoms.

11. The sensor according to any one of claims 1 to 6, wherein: The alkali atoms are cooled by laser light.

12. The sensor according to any one of claims 1 to 6, wherein: The alkali atom is at least one of a rubidium atom and a cesium atom.

13. A detection method comprising: exciting alkali atoms in the vapor cell from a first quantum state to a second quantum state via light of a first wavelength from a first photonic integrated circuit (PIC) forming a wall of the vapor cell, wherein the first photonic integrated circuit (PIC) comprises extraction features configured to direct light of the first wavelength into the vapor cell; Exciting the alkali atoms in the plurality of vapor cells to Rydberg states via light of a second wavelength; detecting a response of the alkali atoms in the Rydberg states to incident electromagnetic radiation; and The output is a signal proportional to the detected response.

14. The detection method according to claim 13, wherein Exciting the alkali atoms in the vapor cell via a first PIC includes: Light at the first wavelength is injected into a waveguide of the first PIC, wherein the waveguide includes the extraction feature.

15. The detection method according to claim 14, wherein Exciting the alkali atoms in the vapor cell via light of the second wavelength includes: injecting light of the second wavelength into a second waveguide of a second PIC; and At least a portion of the injected light at the second wavelength from the second waveguide is extracted into the vapor cell via a second extraction feature of the second PIC.

16. The detection method according to any one of claims 13 to 15, wherein Detecting a response of the alkali atom in the Rydberg state to the incident electromagnetic radiation comprises: After the light of the first wavelength propagates through the vapor cell, the amount of the light of the first wavelength is detected via a photodetector, wherein the response of the alkali atoms in the Rydberg state to the incident electromagnetic radiation includes a change in the electromagnetically induced transparency (EIT) of the alkali atoms to the light of the first wavelength.

17. The detection method according to any one of claims 13 to 15, wherein Detecting a response of the alkali atom in the Rydberg state to the incident electromagnetic radiation comprises: detecting, via an ammeter, a change in current flowing through an electrical circuit comprising at least two electrodes spaced apart within the steam chamber and applying a voltage between the at least two electrodes, wherein the response of the alkali atoms in the Rydberg state to the incident electromagnetic radiation comprises a change in the ionization of the vapor of the alkali atoms.

18. An electromagnetic radiation detection array, comprising: a plurality of vapor chambers arranged in a two-dimensional (2D) array, each vapor chamber comprising vapor of alkali atoms; a first photonic integrated circuit PIC forming a wall of the vapor cell, wherein the first photonic integrated circuit PIC comprises an extraction feature configured to direct light of a first wavelength into each of the plurality of vapor cells and incident on the vapor of the alkali atoms, wherein the light of the first wavelength is configured to excite the alkali atoms from a ground state to a first excited state; and a second PIC configured to direct light of a second wavelength into each of the plurality of vapor cells and incident on the vapor of the alkali atoms, wherein the light of the second wavelength is configured to excite the alkali atoms from the first excited state to a Rydberg state; and A plurality of detectors, each corresponding to one of the plurality of vapor cells and configured to detect a response of the alkali atoms in the Rydberg state to incident electromagnetic radiation.

19. The electromagnetic radiation detection array according to claim 18, wherein: The multiple detectors include multiple photodetectors, each photodetector corresponding to a vapor chamber, wherein the response of the alkali atoms in the Rydberg state to the incident electromagnetic radiation includes a change in the electromagnetically induced transparency (EIT) of the alkali atoms to light of the first wavelength, wherein each photodetector of the multiple photodetectors is configured to detect the amount of light of the first wavelength after the light of the first wavelength propagates through each corresponding vapor chamber of the multiple vapor chambers, and wherein each photodetector of the multiple photodetectors is configured to output a signal proportional to the amount of light of the first wavelength detected.

20. The electromagnetic radiation detection array according to any one of claims 18 to 19, wherein: Each detector of the plurality of detectors comprises: an electrical circuit comprising at least two electrodes spaced apart in corresponding vapor chambers of the plurality of vapor chambers and configured to apply a voltage across the at least two electrodes; and an ammeter configured to measure a current of the circuit comprising the at least two electrodes, wherein the response of the alkali atoms in the Rydberg state to incident electromagnetic radiation comprises a change in the ionization of the vapor of the alkali atoms in the corresponding vapor cell; wherein the ammeter is configured to output a signal related to a change in the current of the circuit in response to a change in the ionization of the vapor of the alkali atoms of the corresponding vapor cell.

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