Transmission grating and laser device using the same, and method of producing transmission grating

A method of producing a transmission grating, the method comprising:

• providing first and second glass plates, each having a first main surface and a second main surface located opposite to the first main surface, the first main surface of each of the glass plates defining a plurality of elongated reverse trapezoidal grooves, each having a reverse trapezoidal shape in a vertical cross-section and being defined by a first wall, a second wall, and a bottom surface, wherein the first walls of the elongated reverse trapezoidal grooves are in parallel to one another and the second walls of the elongated reverse trapezoidal grooves are in parallel to one another, and wherein the elongated reverse trapezoidal grooves are formed at an uniform interval, thus defining a plurality of elongated trapezoidal protrusions, each having a first wall, a second wall, and an upper surface;
• engaging the elongated trapezoidal protrusions of the first glass plate with the elongated reverse trapezoidal grooves of the second glass plate to fit the glass plates to each other;
• and
• closely fitting the first walls of the elongated trapezoidal protrusions with the first walls of the elongated reverse trapezoidal grooves and closely fitting the upper surfaces of the elongated trapezoidal protrusions with the bottom surfaces of the elongated reverse trapezoidal grooves, and bonding the first glass plate to the second glass plate.

A method of producing a transmission grating, the method comprising:

• stacking a plurality of thin glass plates of a same thickness with a predetermined space between each two adjacent thin glass plates to obtain a multi-layered glass structure in which each two adjacent thin glass plates face each other across the space;
• thermally fusing glass on each lateral surface of the multi-layered glass structure to confine the spaces in the multi-layered glass structure;
• supporting the multi-layered glass structure containing the confined spaces, using a glass support structure, at an upper surface, a lower surface, and two lateral surfaces opposite to each other with respect to a central axis that is parallel to the upper surface and the lower surface of the multi-layered structure;
• heating the multi-layered glass structure together with the glass support structure to collectively soften the multi-layered glass structure and the glass support structure, and drawing the multi-layered glass structure together with the glass support structure in a direction parallel to the central axis;
• and
• cutting the drawn multi-layered glass structure together with the glass support structure in a direction parallel to a second plane that is perpendicular to a first plane that includes the central axis and a stacking direction of the thin glass plates.

A method of producing a transmission grating comprising:

• providing a plurality of thin glass plates of a same thickness, each having a first main surface, a second main surface opposite to the first main surface, a first lateral surface, a second lateral surface, a third lateral surface, and a fourth lateral surface;
• the first main surface of each of the thin glass plates defining a plurality of grooves with a predetermined opening width and respectively extending from the first lateral surface side to the third lateral surface side, where the first lateral surface and the third lateral surface are located opposite to each other;
• stacking the plurality of thin glass plates to align longitudinal opening edges of the grooves in a first direction to assemble a multi-layered glass structure;
• thermally fusing an end surface portion of the multi-layered glass structure that includes the first lateral surface of the thin glass plates, an end surface portion of the multi-layered glass structure that includes the second lateral surface of the thin glass plates, an end surface portion of the multi-layered glass structure that includes the third lateral surface of the thin glass plates, and an end surface portion of the multi-layered glass structure that includes the fourth lateral surface of the thin glass plates, to bond adjacent thin glass plates and seal the grooves;
• supporting the multi-layered glass structure containing the sealed grooves with a glass support structure, at the upper surface, the lower surface, the end surface containing the second lateral surfaces of the thin glass plates, and the end surface containing the fourth lateral surfaces of the thin glass plates and located opposite to the end surface containing the second lateral surfaces with respect to a central axis;
• heating the multi-layered glass structure together with the glass support structure to collectively soften the multi-layered glass structure and the glass support structure, and drawing the multi-layered glass structure together with the glass support structure in a direction parallel to the central axis to obtain a drawn multilayered glass structure and a drawn glass support structure;
• and
• cutting the drawn multi-layered glass structure together with the drawn glass support structure in a direction parallel to a first plane that is perpendicular to the central axis to obtain a first cut of the drawn multi-layered glass structure and the drawn glass support structure;
• and
• further cutting the obtained first cut that includes a portion of the drawn multi-layered glass structure and a corresponding portion of the drawn glass support structure in a direction parallel to a second plane that is parallel to the first direction to obtain a second cut.