JP-7855113-B1 - Light source unit

JP7855113B1JP 7855113 B1JP7855113 B1JP 7855113B1JP-7855113-B1

Abstract

[Problem] To provide a light source unit that can suppress light loss while avoiding variations in product quality. [Solution] The laser element 10 has a substrate 11 and a semiconductor laminate 12 formed on the substrate 11 including an active layer 122, and the optical integrated circuit element 20 has a substrate 22 and a unit circuit 30 provided on the substrate 22. The unit circuit 30 has an optical input/output end face 31a facing the first end face 10a of the laser element 10 across a space S, an input/output waveguide 31 extending from the optical input/output end face 31a, and an optical feedback section 40 configured to transmit light of a predetermined wavelength incident from the laser element 10 and return light of a predetermined wavelength to the laser element 10, thereby changing the wavelength of the output light Lo1 within a predetermined wavelength range. The size of the space S in the resonance direction X is smaller than the thickness tL of the active layer 122 and the thickness tW of the input/output waveguide 31 at the optical input/output end face 31a in the thickness direction of the substrate 22. [Selection Diagram] Figure 2

Inventors

鈴木大幾
前北和晃
岩本健汰
間瀬光人
藁科禎久
道垣内龍男
伊藤昭生
齊藤加奈子

Assignees

浜松ホトニクス株式会社

Dates

Publication Date: 20260507
Application Date: 20250402

Claims (13)

A laser element comprising a first substrate and a quantum cascade laser element or interband cascade laser element having a semiconductor laminate formed on the first substrate and including at least an active layer, The system comprises a second substrate and an optical integrated circuit element having a unit circuit provided on the second substrate, The laser element has a first end face and a second end face that face each other in the resonance direction of the laser element. The aforementioned unit circuit is The first end face of the laser element and the optical input/output end face facing each other across space, An input/output waveguide extending from the aforementioned optical input/output end face, The system includes an optical feedback unit that is optically connected to the input/output waveguide and configured to guide light of a predetermined wavelength incident from the first end face of the laser element and return the light of the predetermined wavelength to the laser element, thereby changing the wavelength of the output light within a predetermined wavelength range. A light source unit in which the size of the space in the resonance direction is smaller than the thickness of the active layer in the stacking direction of the semiconductor laminate and the thickness of the input/output waveguide at the optical input/output end face in the thickness direction of the second substrate.
The light source unit according to claim 1, wherein the size of the space in the resonance direction is 1 μm or less.
The light source unit according to claim 1, wherein the size of the space in the resonance direction is one-quarter or less of the shortest wavelength in the predetermined wavelength range.
Having a plurality of the aforementioned laser elements, Each of the plurality of laser elements has a plurality of unit circuits provided in correspondence with each of the plurality of laser elements, The light source unit according to claim 1, wherein the plurality of unit circuits are arranged along an array direction perpendicular to the resonance direction and the thickness direction.
The light source unit according to claim 4, wherein at least one of the plurality of laser elements outputs the output light from the second end face.
The second substrate has an extended portion that extends in the resonance direction toward the side where the laser element is provided, rather than toward the optical input/output end face. The light source unit according to claim 1, wherein the laser element is mounted on the extended portion.
The optical integrated circuit element has a third end face that faces the first end face and includes the optical input/output end face, The light source unit according to claim 1, wherein, when viewed from an array direction perpendicular to the resonance direction and the thickness direction, the third end face has a first portion on which the optical input/output end face is provided, and a second portion that is further away from the first end face than the first portion in the resonance direction.
The optical integrated circuit element has a third end face that faces the first end face and includes the optical input/output end face. The light source unit according to claim 1, wherein, when viewed from the thickness direction, the third end face has a third portion on which the optical input/output end face is provided, and a fourth portion that is further from the first end face than the third portion in the resonance direction.
The light source unit according to claim 1, wherein the width of the active layer in the alignment direction perpendicular to the resonance direction and the thickness direction is greater than the width of the input/output waveguide in the alignment direction at the optical input/output end face.
The light source unit according to claim 1, wherein the width of the active layer in the arrangement direction perpendicular to the resonance direction and the thickness direction is smaller than the width of the input/output waveguide in the arrangement direction at the optical input/output end face.
The light source unit according to claim 1, further comprising a cooling element on which the laser element and the optical integrated circuit element are mounted.
The lens portion that transmits the output light, The light source unit according to claim 1, further comprising a package that houses the laser element and the optical integrated circuit element and also houses or holds the lens portion.
The light source unit according to claim 12, wherein the width of the package in the arrangement direction perpendicular to the resonance direction and the thickness direction is greater than the height of the package in the thickness direction.

Description

This disclosure relates to a light source unit. Conventionally, a light source unit comprising a laser element and an optical integrated circuit (PIC) element including a unit circuit is known (for example, Patent Document 1). In such a light source unit, light is emitted from the laser element to the unit circuit. Of the light incident on the unit circuit, light of a predetermined wavelength is re-incident to the laser element by the optical feedback section of the unit circuit and amplified inside the laser element. The light thus amplified is output as output light to the outside of the device. Special Publication No. 2020-520768 Figure 1 shows the cross-sectional structure of the light source unit according to the first embodiment.Figure 2 shows the cross-sectional structure of the light source unit along the line II-II in Figure 1.Figure 3 shows an example configuration of a laser element and a corresponding unit circuit.Figure 4 shows an example of a waveguide configuration.Figure 5 shows the cross-sectional structure of the portion where the laser element and the optical integrated circuit element face each other.Figure 6 shows an example of the arrangement of power monitors.Figure 7 shows an example of the control configuration of a light source unit.Figure 8 shows an example of pulse timing.Figure 9 shows another example of pulse timing.Figure 10 shows an example of the configuration of an output waveguide.Figure 11 shows a first modified example of the third end face.Figure 12 shows a second modified example of the third end face.Figure 13 shows the cross-sectional structure of the light source unit according to the second embodiment.Figure 14 is a plan view showing the configuration of an optical integrated circuit element in the second embodiment.Figure 15 shows an example configuration of a laser element and a corresponding unit circuit in the second embodiment.Figure 16 shows a first modified example of the wavelength adjustment section.Figure 17 shows a second modified example of the wavelength adjustment section.Figure 18 shows a first modified example of a loop-type optical feedback section.Figure 19 shows a second modified example of a loop-type optical feedback section.Figure 20 shows a modified example of the optical integrated circuit element in the second embodiment.Figure 21 shows a modified example of a waveguide. Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant explanations will be omitted. The drawings may be simplified or exaggerated in part for ease of understanding. Therefore, the dimensional ratios of the embodiment are not limited to those shown in the drawings. [First Embodiment] As shown in Figures 1 and 2, the light source unit 1 of the first embodiment comprises a plurality of laser elements 10 and an optical integrated circuit element 20. As shown in Figure 2, the optical integrated circuit element 20 has a substrate 22 (second substrate) and a plurality of unit circuits 30 (301-304) provided on the substrate 22 (Ge layer 25, described later). As shown in Figure 3, the unit circuits 30 are composed of various optical elements, including waveguides, provided on the substrate 22 (Ge layer 25). In this embodiment, one unit circuit 30 corresponds to one laser element 10. Hereinafter, the thickness direction of the substrate 22 will be referred to as the thickness direction Z, the common resonance direction of the multiple laser elements 10 will be referred to as the resonance direction X, and the direction perpendicular to the thickness direction Z and the resonance direction X (in this embodiment, the direction in which the multiple laser elements 10 are arranged) will be referred to as the arrangement direction Y. Multiple laser elements 10 and optical integrated circuit elements 20 are housed within the package 2. In the light source unit 1, the package 2 further houses a cooling element 3, a carrier substrate 4, a lens section 5, an output window 6, and a temperature sensor 7, among other components. Package 2 has a bottom wall 2a, a side wall 2b, and a top wall 2c. The bottom wall 2a is a rectangular plate-shaped member whose resonance direction X is the longitudinal direction and whose arrangement direction Y is the short direction. The side wall 2b is connected to the edge of the bottom wall 2a when viewed from the thickness direction Z and extends in the thickness direction Z. That is, when viewed from the thickness direction Z, the side wall 2b is formed in an annular shape (rectangular in this embodiment) so as to surround the internal space in which the optical integrated circuit element 20 etc. is housed. In other words, in this embodiment, the side wall 2b is formed in a rectangular cylindrical shape. The top wall 2c is a member that closes the opening on the side of the side w