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 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 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: 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: 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.

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, 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 device is disclosed for providing a reference frequency of light. The device includes a housing having a first opening and a second opening. A first optical window covers the first opening and is coupled to the housing by a first ceramic bond that forms a hermetic seal around the first opening. A second optical window covers the second opening and is coupled to the housing by a second ceramic bond that forms a hermetic seal around the second opening. The device also includes an etalon disposed within an evacuated volume enclosed by at least the housing, the first optical window, and the second optical window. The device additionally includes one or more supports suspending the etalon in the evacuated volume. The one or more supports are formed of a material having a thermal conductivity no greater than 5 W/m·K at room temperature.

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.

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 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 method of manufacturing a vapor cell is presented. The method includes obtaining a dielectric body having a surface that defines an opening to a cavity in the dielectric body. The method also includes obtaining an optical window that includes a surface. The surfaces of the dielectric body and the optical window are altered to include, respectively, a first plurality of hydroxyl ligands and a second plurality of hydroxyl ligands. The method additionally includes disposing a vapor, or a source of the vapor, into the cavity. The altered surface of the dielectric body is contacted to the altered surface of the optical window to form a seal around the opening to the cavity. The seal includes metal-oxygen bonds formed by reacting the first plurality of hydroxyl ligands with the second plurality of hydroxyl ligands during contact of the altered surfaces.