Abstract: In a general aspect, a vapor cell includes a body defined by a stack of layers that includes electrically conductive layers and electrically insulating layers. The stack of layers are bonded to each other and have first and second end layers at respective opposite ends of the body. The stack of layers also has intermediate layers between the first and second end layers that define an internal cavity of the body. The internal cavity extends through the body between the first and second end layers and includes a vapor or a source of the vapor disposed therein. Adjacent electrically conductive layers are separated by at least one electrically insulating layer. Moreover, each electrically conductive layer defines an electrode of the vapor cell and includes a contact surface on an exterior side of the body. The contact surface defines an electrical contact of the electrode.

Abstract: In a general aspect, a method includes interacting a beam of light with a vapor in a vapor cell. The vapor cell includes a body defined by a stack of layers that includes electrically conductive layers and electrically insulating layers. The stack of layers are bonded to each other and have first and second end layers at respective opposite ends of the body. The stack of layers also has intermediate layers between the first and second end layers that define an internal cavity of the body. A vapor is disposed in the internal cavity. The method includes applying respective voltages to one or more electrodes to alter an electric field in the internal cavity. The method also includes measuring one or both of an ion signal based on charged particles in the vapor and an optical property of the beam of light after interacting with the vapor.

Abstract: In a general aspect, a communication system comprises a first station and a second station. The first station includes a photonic crystal maser, a laser subsystem, and a tracking subsystem. A photonic crystal structure of the photonic crystal maser is formed of dielectric material and has an array of cavities and an elongated slot. The elongated slot is disposed in a defect region of the array of cavities. The photonic crystal maser also includes a vapor disposed in the elongated slot and operable to emit a target RF electromagnetic radiation in response to receiving an optical signal. The array of cavities and the elongated slot define a waveguide configured to form the target RF electromagnetic radiation, when emitted, into a beam. The second station includes a receiver configured to couple to the beam of target RF electromagnetic radiation.

Abstract: In a general aspect, a photonic crystal maser includes a dielectric body having an array of cavities ordered periodically to define a photonic crystal structure in the dielectric body. The dielectric body also includes a region in the array of cavities defining a defect in the photonic crystal structure. An elongated slot through the region extends from a slot opening in a surface of the dielectric body at least partially through the dielectric body. The elongated slot and the array of cavities define a waveguide of the dielectric body. The dielectric body additionally includes an input coupler aligned with an end of the elongated slot and configured to couple a reference radiofrequency (RF) electromagnetic radiation to the waveguide. The photonic crystal maser also includes a vapor or source of the vapor in the elongated slot and an optical window covering the elongated slot.

Abstract: In a general aspect, a communication system comprises a first station and a second station. Each station includes a transceiver and a control subsystem. The transceiver includes having one or more photonic crystal masers and one or more photonic crystal receivers. The control subsystem includes one or more lasers optically coupled to the one or more photonic crystal masers and the one or more photonic crystal receivers. The control subsystem also includes modulation electronics in communication with the one or more lasers and configured to control one or more properties of a first input optical signal received by each photonic crystal maser. The control subsystem additionally includes demodulation electronics in communication with the one or more lasers and configured to control one or more properties of a second input optical signal received by each photonic crystal receiver.

Abstract: In a general aspect, a vapor cell includes a body defined by a stack of layers bonded to each other. The stack of layers includes a first end layer disposed at a first end of the body and a second end layer disposed at a second, opposite end of the body. Intermediate layers extend between the first and second end layers and define an internal cavity extending through the body between the first end layer and the second end layer. The stack of layers also includes first and second sets of tabs. The first set of tabs extends outward from the intermediate layers on a first exterior side of the body, and the second set of tabs extends outward from the intermediate layers on a second exterior side of the body. The vapor cell also includes a vapor or a source of the vapor disposed in the internal cavity.

Abstract: In a general aspect, a vapor cell is presented that includes a dielectric body. The dielectric body has a surface that defines an opening to a cavity in the dielectric body. The vapor cell also includes a vapor or a source of the vapor in the cavity of the dielectric body. An optical window covers the opening of the cavity and has a surface bonded to the surface of the dielectric body to form a seal around the opening. The seal includes metal-oxygen bonds formed by reacting a first plurality of hydroxyl ligands on the surface of the dielectric body with a second plurality of hydroxyl ligands on the surface of the optical window.

Abstract: In a general aspect, a vapor cell includes a body defined by a stack of layers bonded to each other. The stack of layers includes a first end layer disposed at a first end of the body and a second end layer disposed at a second, opposite end of the body. Intermediate layers extend between the first and second end layers and define an internal cavity extending through the body between the first end layer and the second end layer. The stack of layers also includes first and second sets of tabs. The first set of tabs extends outward from the intermediate layers on a first exterior side of the body, and the second set of tabs extends outward from the intermediate layers on a second exterior side of the body. The vapor cell also includes a vapor or a source of the vapor disposed in the internal cavity.

Abstract: In a general aspect, a vapor cell includes a body defined by a stack of layers bonded to each other. The stack of layers includes a first end layer disposed at a first end of the body and a second end layer disposed at a second, opposite end of the body. Intermediate layers extend between the first and second end layers and define an internal cavity extending through the body between the first end layer and the second end layer. Each intermediate layer includes a through-hole that defines a portion of the internal cavity through the intermediate layer. The vapor cell also includes a vapor or a source of the vapor disposed in the internal cavity.

Abstract: In a general aspect, a vapor cell includes a body defined by a stack of layers bonded to each other. The stack of layers defines an array of cavities that includes first and second subsets of cavities. The first subset of cavities extends through intermediate layers of the stack of layers and the second subset of cavities extends entirely through the stack of layers. The vapor cell includes a vapor or a source of the vapor disposed in each of the first subset of cavities. The stack of layers includes a first end layer disposed at a first end of the body and a second end layer disposed at a second, opposite end of the body. The intermediate layers are positioned between the first and second end layers.

Abstract: In a general aspect, a photonic crystal maser includes a dielectric body having an array of cavities ordered periodically to define a photonic crystal structure in the dielectric body. The dielectric body also includes a region in the array of cavities defining a defect in the photonic crystal structure. An elongated slot through the region extends from a slot opening in a surface of the dielectric body at least partially through the dielectric body. The array of cavities and the elongated slot define a waveguide having a waveguide mode. The photonic crystal maser also includes a vapor or source of the vapor in the elongated slot and a laser configured to generate an optical signal capable of exciting one or more input electronic transitions of the vapor.

Abstract: In a general aspect, a system for generating radio frequency (RF) electromagnetic radiation includes a maser having a photonic crystal structure and a vapor. The photonic crystal structure is formed of dielectric material and includes an array of cavities having a defect region disposed therein and an elongated slot disposed in the defect region. The array of cavities and the elongated slot define a waveguide having a waveguide mode. The vapor is disposed in the elongated slot and includes one or more input electronic transitions and an output electronic transition coupled to the one or more input electronic transitions. The output electronic transition is operable to emit a target RF electromagnetic radiation and is resonant with the waveguide mode. The system also includes a laser system configured to provide input optical signals to the elongated slot and signal processing electronics in communication with the laser system.

Abstract: In a general aspect, a system is disclosed for sensing radio frequency (RF) electromagnetic radiation. The system includes a receiver formed of dielectric material. The receiver includes a photonic crystal structure having an elongated slot disposed therein. The receiver also includes an antenna structure extending from the photonic crystal structure and configured to couple to a target RF electromagnetic radiation having a frequency in a range from 100 MHz-1 THz. A vapor or source of the vapor in the elongated slot. The system also includes a laser system configured to provide input optical signals to the elongated slot that interact with one or more electronic transitions of the vapor. The system additionally includes an optical detection system configured to detect the target RF electromagnetic radiation based on output optical signals from the elongated slot.

Abstract: In a general aspect, vapor cells are disclosed that include a dielectric body having a first surface and a second surface. The dielectric body includes a plurality of cavities extending from the first surface to the second surface and ordered periodically to define a photonic crystal structure in the dielectric body. Each cavity has a first opening defined by the first surface and a second opening defined by the second surface. The photonic crystal structure has a photonic band gap. The vapor cells additionally include a first optical window covering the first openings and having a surface bonded to the first surface of the dielectric body to form a seal around each of the first openings. A second optical window covers the second openings and has a surface bonded to the second surface of the dielectric body to form a seal around each of the second openings.

Abstract: In a general aspect, a receiver is disclosed for sensing radio frequency (RF) electromagnetic radiation. The receiver includes a dielectric body having an array of cavities ordered periodically to define a photonic crystal structure in the dielectric body. The dielectric body also has a region in the array of cavities that defines a defect in the photonic crystal structure. An elongated slot through the region extends from a slot opening in a surface of the dielectric body at least partially through the dielectric body. The receiver also includes a vapor or a source of the vapor in the elongated slot as well as an optical window covering the elongated slot. The optical window has a window surface bonded to the surface of the dielectric body to form a seal about the slot opening.

Abstract: In a general aspect, a radar system includes a photonic crystal receiver. In some aspects, the radar system includes a transmitter station configured to emit probe signals of RF electromagnetic radiation into a region. The radar system also includes a receiver station configured to process return signals of RF electromagnetic radiation from the region. The return signals are based on probe signals scattered from one or more objects in the region. The receiver station includes a photonic crystal receiver formed of dielectric material. The photonic crystal receiver includes an antenna structure, a photonic crystal structure, and a vapor. The receiver station also includes an optical system and a data processing subsystem. The optical system is configured to generate spectroscopic data based on optical signals from the photonic crystal receiver. The data processing subsystem is configured to generate a time series of property data based on the spectroscopic data.

Abstract: In a general aspect, a radar system includes a photonic crystal receiver. In some aspects, the radar system includes a transmitter station configured to emit probe signals of RF electromagnetic radiation into a region. The radar system also includes a receiver station configured to process return signals of RF electromagnetic radiation from the region. The return signals are based on probe signals scattered from one or more objects in the region. The receiver station includes a photonic crystal receiver formed of dielectric material. The photonic crystal receiver includes an antenna structure, a photonic crystal structure, and a vapor. The receiver station also includes an optical system and a data processing subsystem. The optical system is configured to generate spectroscopic data based on optical signals from the photonic crystal receiver. The data processing subsystem is configured to generate a time series of property data based on the spectroscopic data.

Abstract: In a general aspect, a receiver is disclosed for sensing radio frequency (RF) electromagnetic radiation. The receiver includes a dielectric body having an array of cavities ordered periodically to define a photonic crystal structure in the dielectric body. The dielectric body also has a region in the array of cavities that defines a defect in the photonic crystal structure. An elongated slot through the region extends from a slot opening in a surface of the dielectric body at least partially through the dielectric body. The receiver also includes a vapor or a source of the vapor in the elongated slot as well as an optical window covering the elongated slot. The optical window has a window surface bonded to the surface of the dielectric body to form a seal about the slot opening.

Abstract: In a general aspect, a system is disclosed for sensing radio frequency (RF) electromagnetic radiation. The system includes a receiver formed of dielectric material. The receiver includes a photonic crystal structure having an elongated slot disposed therein. The receiver also includes an antenna structure extending from the photonic crystal structure and configured to couple to a target RF electromagnetic radiation having a frequency in a range from 100 MHz-1 THz. A vapor or source of the vapor in the elongated slot. The system also includes a laser system configured to provide input optical signals to the elongated slot that interact with one or more electronic transitions of the vapor. The system additionally includes an optical detection system configured to detect the target RF electromagnetic radiation based on output optical signals from the elongated slot.

Abstract: Vapor cells are disclosed that include a dielectric body having a first surface and a second surface. The dielectric body includes a plurality of walls extending from the first surface to the second surface. A perimeter wall surrounds an open volume of the dielectric body and interconnected walls are arranged within the open volume to partition the open volume into a plurality of cells. Each cell has a first opening defined by the first surface and a second opening defined by the second surface. The vapor cells additionally include a first optical window covering the first openings and having a surface bonded to the first surface of the dielectric body to form a seal around each of the first openings. A second optical window covers the second openings and has a surface bonded to the second surface of the dielectric body to form a seal around each of the second openings.