CN101867153A - Ring Cavity Photonic Crystal Vertical Cavity Surface Emitting Laser - Google Patents

Abstract

The invention discloses a ring-cavity photonic crystal vertical-cavity surface-emitting laser (PC-VCSEL), which is characterized by comprising a lower electrode (1), an n-type substrate (2), lower DBR (3), an active area (4), an oxide layer (5), upper DBR (6) on which air holes are carved, a p-type cover layer (7), an upper ring electrode (8), an air hole area (9) and a ring light-exiting hole area (10) in sequence from bottom to top, wherein the air hole area on the surface of the upper DBR of the laser is a high loss area; the ring area enclosed by the air holes is a light output area; and the electrodes of the laser are evaporated on the surface of the p-type cover layer of the upper DBR and the lower surface of the n-type substrate. The laser can realize coherent coupling output and the output power and the beam quality of the laser are improved.

Description

Ring Cavity Photonic Crystal Vertical Cavity Surface Emitting Laser

technical field

The invention relates to the technical field of semiconductor optoelectronic devices, in particular to a ring cavity photonic crystal vertical cavity surface emitting laser.

Background technique

Vertical cavity surface emitting laser (VCSEL) is widely used in optical communication, optical storage, optical interconnection, solid-state lighting, Fields such as laser printing and biosensing are widely used and have attracted great interest and attention. In many applications, VCSEL single-mode high-power operation is required. When the oxidation aperture is small, it is easy to achieve single-mode operation, but the output power is limited. Experimental results show that when the oxide aperture is reduced to 3μm, the VCSEL with a wavelength of 850nm can achieve single-mode output, but its maximum output power is less than 3mW. In order to increase the output power, it is necessary to increase the size of the oxide aperture, but the thermal effect and the phenomenon of space burning holes will lead to the generation of high-order modes, which will deteriorate the performance of the device.

In order to realize the single-mode high-power VCSEL, the mode-based selective loss mechanism is as reported in literature 1: "H.Martinsson, J.A.Vukuˇsi′c, K.J.Ebeling, et al., IEEE PHOTONICSTECHNOLOGY LETTERS, 1999(11): 1536" Etching structure, literature 2: "Delai Zhou, Luke J. Mawst, IEEE JOURNAL OF QUANTUM ELECTRONICS, 2002(38): 1599" reported anti-waveguide structure, and literature 3: "Akio Furukawa, Satoshi Sasaki, Mitsunari Hoshi, Atsushi Matsuzono, et al., Appl. Phys. Lett. 2004 (85): 5161 "reported triangular pore-like structure. These three structures have achieved single-mode high-power lasing, but precise control is required and the manufacturing process is complicated.

Photonic crystals provide an excellent platform for improving the performance of optoelectronic devices, and photonic crystal vertical cavity surface emitting lasers are a successful example. In the photonic crystal vertical cavity surface emitting laser (PC-VCSEL), the oxidation aperture is larger than the light exit aperture, so the oxidation aperture only limits the current, and the light field is limited by the photonic crystal air hole. We know that in a vertical cavity surface emitting laser, the output power is proportional to the area of the active region, so in a photonic crystal vertical cavity surface emitting laser, the size of the defect cavity determines the output power. Since the output power of a single-defect cavity is always limited, and when the light exit aperture is changed to a 7-hole defect cavity, high-order modes will be generated, so literature 4: "James J.Raftery, Jr., Ann C.Lehman, Aaron J.Danner, et al., Appl.Phys.Lett.2006(89): 081119" reported that 2×1 and 2×2 arrays of photonic crystal vertical cavity surface-emitting lasers were fabricated by fine-tuning the size of the air holes in the coupling region, and the coherent The output-coupled PC-VCSEL has a main lobe at the origin in its far-field distribution. However, no matter it is a PC-VCSEL with dual-cavity coupling or four-cavity coupling, its output power is still limited due to the limited area of its active region.

Contents of the invention

(1) Technical problems to be solved

In view of this, the main purpose of the present invention is to provide a ring-cavity photonic crystal vertical cavity surface-emitting laser, to overcome the bottleneck of single-mode output power of single-defect photonic crystal vertical cavity surface-emitting lasers, and to achieve low beam density based on coherent coupling. The purpose of the divergence angle output.

(2) Technical solution

In order to achieve the above object, the present invention provides a ring cavity photonic crystal vertical cavity surface emitting laser, the vertical cavity surface emitting laser is sequentially composed of a lower electrode 1, an n-type substrate 2, a lower DBR3, an active region 4, The oxide layer 5, the upper DBR6 with air holes carved, the p-type cover layer 7 and the upper ring electrode 8, the air hole area 9 and the ring light exit hole area 10 are formed.

In the above solution, the air holes in the air hole region 9 are photonic crystal air holes arranged in a triangular lattice, or photonic crystal air holes arranged in a tetragonal lattice.

In the above solution, the photonic crystal air holes arranged in a triangular lattice or the photonic crystal air holes arranged in a tetragonal lattice have cells of circular air hole type, elliptical air hole type or square air hole type.

In the above solution, the annular light exit hole area 10 is an area surrounded by air holes.

In the above solution, the air hole area 9 is a high loss area.

In the above solution, the designed oxidation aperture of the vertical cavity surface emitting laser is larger than the outer diameter of the annular light exit hole.

In the above solution, the etching depth of the air holes in the air hole area 9 is 40%-80% of the thickness of the upper DBR3.

In the above solution, the upper ring electrode 8 is evaporated on the surface of the p-type cap layer 7 , and the lower electrode 1 is evaporated on the lower surface of the n-type substrate 2 .

In the above solution, the material used for the upper ring electrode 8 is TiAu alloy, and the material used for the lower electrode 1 is AuGeNiAu alloy.

In the above solution, the reflectivity of the lower DBR3 is higher than the reflectivity of the upper DBR6.

In the above solution, the working wavelength of the vertical cavity surface emitting laser covers the deep ultraviolet to far infrared band.

(3) Beneficial effects

As can be seen from the foregoing technical solutions, the present invention has the following beneficial effects:

1. The ring-cavity photonic crystal vertical cavity surface-emitting laser provided by the present invention increases the area of the active region and improves the output power, and is expected to achieve a power output of the order of 10 mW.

2. The ring cavity photonic crystal vertical cavity surface emitting laser provided by the present invention can be simplified into a 2×1 vertical cavity surface emitting laser array, which can realize coherent coupling output and output low divergence angle while increasing the output power beam.

3. The annular cavity photonic crystal vertical cavity surface emitting laser provided by the present invention not only reduces the differential resistance, improves the efficiency, but also prolongs the service life and reliability of the device due to its large oxidation aperture.

Description of drawings

FIG. 1 is a schematic structural diagram of the ring cavity photonic crystal vertical cavity surface emitting laser provided by the present invention. The z coordinate direction in the figure represents the vertical direction of the device; the x and y coordinate directions represent the horizontal direction of the device;

Fig. 2 is a top view schematic diagram of the surface topography of the ring cavity photonic crystal surface emitting laser of the ring cavity photonic crystal vertical cavity surface emitting laser provided by the present invention with the upper DBR engraved with the circular air holes arranged in triangular lattice. Holes can also be made larger or smaller;

Fig. 3 is a top view schematic diagram of the surface topography of the ring cavity photonic crystal surface emitting laser whose upper DBR of the ring cavity photonic crystal vertical cavity surface emitting laser provided by the present invention is engraved with circular air holes arranged in a tetragonal lattice. Holes can also be made larger or smaller;

Fig. 4 is the scanning electron micrograph of the upper DBR of this ring cavity photonic crystal vertical cavity surface emitting laser provided by the first example of the present invention, and its center hole is enlarged;

Fig. 5 is the measured power-current-voltage curve of the ring cavity photonic crystal vertical cavity surface emitting laser provided in the first example of the present invention.

Fig. 6 shows the far-field distribution measured at a current of 34 mA for the ring-cavity photonic crystal vertical cavity surface-emitting laser provided in the first example of the present invention.

In the figure, 1 is the lower electrode, 2 is the n-type substrate, 3 is the lower DBR, 4 is the active region, 5 is the oxide layer, 6 is the upper DBR, 7 is the p-type capping layer, 8 is the upper ring electrode, 9 10 is an air hole area, and 10 is an annular light exit area.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

As shown in Figure 1, Figure 1 is the ring-cavity photonic crystal vertical cavity surface-emitting laser provided by the present invention, the vertical cavity surface-emitting laser is sequentially composed of a lower electrode 1, an n-type substrate 2, a lower DBR3, an The source region 4, the oxide layer 5, the upper DBR6 engraved with air holes, the p-type cover layer 7, the upper ring electrode 8, the air hole region 9 and the ring light exit hole region 10 are formed.

The air holes in the air hole region 9 are photonic crystal air holes arranged in a triangular lattice, or photonic crystal air holes arranged in a tetragonal lattice.

The photonic crystal air holes arranged in a triangular lattice or the photonic crystal air holes arranged in a tetragonal lattice have cells of circular air hole type, elliptical air hole type or square air hole type.

The annular light exit area 10 is an area surrounded by air holes.

The air hole area 9 is a high loss area.

The designed oxidation aperture of the vertical cavity surface emitting laser is larger than the outer diameter of the annular light exit hole.

The etching depth of the air holes in the air hole area 9 is 40%-80% of the thickness of the upper DBR3.

The upper ring electrode 8 is evaporated on the surface of the p-type capping layer 7 , and the lower electrode 1 is evaporated on the lower surface of the n-type substrate 2 .

The material used for the upper ring electrode 8 is TiAu alloy, and the material used for the lower electrode 1 is AuGeNiAu alloy.

The reflectivity of the lower DBR3 is higher than that of the upper DBR6.

The working wavelength of the vertical cavity surface emitting laser in this design covers the deep ultraviolet to far infrared band.

As shown in Fig. 2 and Fig. 3, Fig. 2 and Fig. 3 are respectively the annular cavity of the photonic crystal circular air holes in the upper DBR of the photonic crystal vertical cavity surface-emitting laser provided by the present invention. Schematic diagram of top view of surface topography of photonic crystal vertical cavity surface emitting laser and top view schematic diagram of surface topography of ring cavity photonic crystal vertical cavity surface emitting laser with photonic crystal circular air holes engraved with tetragonal lattice arrangement on the upper DBR. In the figure, 9 is a photonic crystal area, and 10 is an annular light exit hole. The photonic crystal period of the photonic crystal region 9 is Λ, the duty ratio (the ratio of the diameter of the air hole to the period) is d/Λ, and the etching depth is h.

Based on the ring-cavity photonic crystal vertical-cavity surface-emitting laser described in FIG. 1 , FIG. 2 and FIG. 3 , the ring-cavity photonic crystal vertical-cavity surface-emitting laser provided by the present invention will be further described in detail below in conjunction with specific embodiments.

In this embodiment, the operating wavelength of the ring cavity photonic crystal vertical cavity surface emitting laser is 0.85 μm. A schematic top view of the surface topography of the upper DBR of the vertical cavity surface emitting laser of this example is shown in FIG. 4 . In this example, the lower electrode is AuGeNiAu alloy, the upper electrode is TiAu alloy, the lower DBR is 34.5 pairs of n-type Al _0.12 Ga _0.88 As/Al _0.9 Ga _0.1 As, the active region is 3 pairs of GaAs/AlGaAs quantum wells, and the oxidation aperture is 25μm, the upper DBR is 20.5 pairs of p-type Al _0.12 Ga _0.88 As/Al _0.9 Ga _0.1 As; the surface of the upper DBR is engraved with a photonic crystal circular air hole pattern arranged in a triangular lattice, the diameter of the central hole is 3.8μm, and the central air hole The nearest ring of air holes is removed to form a ring-shaped light exit hole. The period of the photonic crystal is 5 μm, the diameter of the air hole is 3 μm, and the etching depth is 10 pairs of DBR; the surrounding of the light exit aperture is a high loss area formed by the photonic crystal air hole .

The measurement results of this embodiment are shown in FIG. 5 and FIG. 6 . Fig. 5 is a measured power-current-voltage curve of the ring-cavity photonic crystal vertical cavity surface-emitting laser provided in the first example of the present invention, and its maximum output power is 4.6 milliwatts. Fig. 6 is the far-field distribution measured at a current of 34 mA for the ring-cavity photonic crystal vertical-cavity surface-emitting laser provided in the first example of the present invention, and its half-maximum width is 7.2 degrees.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (11)

1. A ring-cavity photonic crystal vertical cavity surface-emitting laser is characterized in that, the vertical cavity surface-emitting laser is successively composed of lower electrode (1), n-type substrate (2), lower DBR (3), and Source region (4), oxide layer (5), upper DBR (6) engraved with air holes, p-type cover layer (7) and upper ring electrode (8), air hole area (9) and ring light exit hole area ( 10) Composition. 2. ring cavity photonic crystal vertical cavity surface emitting laser according to claim 1, is characterized in that, the air hole in the air hole area (9) is the photonic crystal air hole of triangular lattice arrangement, or tetragonal crystal Grid-arranged photonic crystal air holes. 3. ring cavity photonic crystal vertical cavity surface emitting laser according to claim 2, is characterized in that, the photonic crystal air hole of described triangular lattice arrangement or the photonic crystal air hole of tetragonal lattice arrangement, its cell is circular Air hole pattern, oval air hole pattern or square air hole pattern. 4. The annular cavity photonic crystal vertical cavity surface emitting laser according to claim 1, characterized in that, the annular light exit area (10) is an area surrounded by air holes. 5. The ring cavity photonic crystal vertical cavity surface emitting laser according to claim 1, characterized in that the air hole region (9) is a high loss region. 6 . The ring-cavity photonic crystal vertical cavity surface-emitting laser according to claim 1 , wherein the designed oxidation aperture of the vertical-cavity surface-emitting laser is larger than the outer diameter of the ring-shaped light exit hole. 7. The ring cavity photonic crystal vertical cavity surface emitting laser according to claim 1, wherein the etching depth of the air holes in the air hole area (9) is 40% to 80% of the thickness of the upper DBR (3). %. 8. ring cavity photonic crystal vertical cavity surface emitting laser according to claim 1, is characterized in that, described upper ring electrode (8) is evaporated on the surface of p-type cover layer (7), and described lower electrode (1 ) is evaporated on the lower surface of the n-type substrate (2). 9. The ring cavity photonic crystal vertical cavity surface emitting laser according to claim 1, characterized in that the material used for the upper ring electrode (8) is TiAu alloy, and the material used for the lower electrode (1) is AuGeNiAu alloy. 10. The ring cavity photonic crystal vertical cavity surface emitting laser according to claim 1, characterized in that, the reflectivity of the lower DBR (3) is higher than the reflectivity of the upper DBR (6). 11. The ring-cavity photonic crystal vertical cavity surface emitting laser according to claim 1, characterized in that the working wavelength of the vertical cavity surface emitting laser covers deep ultraviolet to far infrared bands.

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