CN216903721U - Vertical cavity surface emitting laser array with tunable wavelength - Google Patents
Vertical cavity surface emitting laser array with tunable wavelength Download PDFInfo
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- CN216903721U CN216903721U CN202220143776.9U CN202220143776U CN216903721U CN 216903721 U CN216903721 U CN 216903721U CN 202220143776 U CN202220143776 U CN 202220143776U CN 216903721 U CN216903721 U CN 216903721U
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Abstract
The utility model discloses a wavelength tunable vertical cavity surface emitting laser array, which is formed by vertical cavity surface emitting lasers with different inherent thermal resistances, and realizes the wavelength tuning of the emitted laser by selecting the emitted laser of different vertical cavity surface emitting lasers or adjusting the input current of each vertical cavity surface emitting laser or combining the above methods, and finally realizes the wavelength tuning of the emitted laser of the array by leading the junction temperature of each vertical cavity surface emitting laser to be different. The utility model has great application potential in dense wavelength division multiplexing optical networks, electronic communication and computer optical interconnection.
Description
Technical Field
The utility model relates to a vertical cavity surface emitting laser array with tunable wavelength.
Background
The Vertical-Cavity Surface-Emitting Laser (VCSEL) has the advantages of small size, wide corresponding frequency band, small temperature drift, low threshold current, single longitudinal mode emission, small divergence angle, high modulation rate, circular light spot of emitted Laser, easy coupling with optical fiber, simple packaging, easy two-dimensional integration, long service life and the like, and has good application prospect in the fields of optical fiber communication, atomic clocks, 3D sensing, automobile radar and the like. The laser light of the vertical cavity surface emitting laser is emitted from the top surface or the bottom surface perpendicular to the chip surface, and the emitting direction is determined by the laser wavelength.
The VCSEL has a structure with upper and lower Distributed Bragg Reflectors (DBRs) divided into a reflective region and an exit region, the reflective region has a reflectivity of 99.9% or more, the exit region has a reflectivity of 99% or more, and the difference determines the exit position of the final wavelength. The upper and lower distributed Bragg reflectors wrap the active layer in the middle to form a laser resonant cavity, so that light which reciprocates in the direction vertical to the cavity generates resonant amplification, and finally the laser reaches a threshold value to emit laser. DBRs are made by stacking a plurality of materials having greatly different refractive indices and lattice constant matching, and it is common to stack GaAs and AlAs alternately. In such a DBR, it is preferable to make the energy band gap larger than the resonance wavelength to avoid light absorption.
With the large-scale application of VCSELs in Dense Wavelength Division Multiplexing (DWDM) optical fiber communication systems, the demand for wavelength tunable VCSELs is increasing.
Disclosure of Invention
The purpose of the utility model is as follows: in view of the above prior art, a wavelength tunable vertical cavity surface emitting laser array is proposed for realizing wavelength tuning of emitted laser.
The technical scheme is as follows: the vertical cavity surface emitting laser array with tunable wavelength has different inherent heat resistances, and the vertical cavity surface emitting lasers are connected via common anode and connected via driving circuit to the cathodes.
Furthermore, the oxide aperture of the oxide confinement layer of each vertical cavity surface emitting laser is different.
Further, the vertical cavity surface emitting laser includes:
a substrate;
a lower electrode formed on the lower surface of the substrate;
a buffer layer formed on the upper surface of the substrate;
a lower distributed Bragg reflector formed on the upper surface of the buffer layer;
an active region formed on an upper surface of the lower DBR;
an oxidation limiting layer formed on the upper surface of the active region;
an upper distributed Bragg reflector formed on the upper surface of the oxide confinement layer;
and an upper electrode formed on the upper surface of the upper DBR.
Further, a driving circuit for driving the array includes:
the charging control module is used for controlling the charging of the circuit;
the energy storage module is used for storing electric energy;
the discharge control module is used for controlling the energy storage module to discharge;
and the main control circuit module is used for outputting a charging control signal and a discharging control signal.
Further, the lower distributed bragg reflector and the upper distributed bragg reflector are formed by alternately laminating compound semiconductor layers having different refractive indexes.
Further, the active region includes an active layer which is a compound semiconductor layer having a multiple quantum well structure.
Has the advantages that: the vertical cavity surface emitting laser array is composed of vertical cavity surface emitting lasers with different inherent thermal resistances, and the wavelength tuning of the emitted laser is realized by selecting the emitted laser of different vertical cavity surface emitting lasers or adjusting the input current of each vertical cavity surface emitting laser, or the wavelength tuning of the emitted laser of the array is realized by combining the above methods.
Specifically, in the first wavelength tunable VCSEL array provided by the present invention, the oxide aperture of the oxide confinement layer is designed to make the intrinsic thermal resistance of each VCSEL different, so that when the same current is input, the junction temperature of each VCSEL is different, which may result in different lasing wavelengths of the VCSELs, thereby implementing wavelength tuning.
Furthermore, each VCSEL can be individually addressed and driven, and the junction temperature of the VCSEL can be further adjusted by changing the input current of the VCSEL, wherein different junction temperatures can bring different lasing wavelengths of the VCSEL, so that the wavelength tuning is formed.
Drawings
FIG. 1 is a schematic cross-sectional view of a VCSEL in the present invention;
FIG. 2 is a schematic diagram of an array structure of a common anode connection in the example.
Detailed Description
The utility model is further explained below with reference to the drawings.
The vertical cavity surface emitting laser array with tunable wavelength has different inherent heat resistances, common anode connection of the vertical cavity surface emitting lasers, driving circuit connected to the cathodes of the vertical cavity surface emitting lasers, and selective control of the cathode discharge of different vertical cavity surface emitting lasers to output different wavelength outgoing laser.
As shown in fig. 1, the vertical cavity surface emitting laser includes:
a substrate 1;
a lower electrode 2 formed on the lower surface of the substrate 1;
a buffer layer 3 formed on the upper surface of the substrate 1;
a lower distributed Bragg reflector (4) formed on the upper surface of the buffer layer (3);
an active region 5 formed on the upper surface of the lower DBR 4;
an oxide confinement layer 6 formed on the upper surface of the active region 5;
an upper distributed Bragg reflector (7) formed on the upper surface of the oxide confinement layer (6);
and an upper electrode 8 formed on an upper surface of the upper DBR 7.
The lower distributed bragg reflector 4 and the upper distributed bragg reflector 7 are formed by alternately laminating compound semiconductor layers with different refractive indexes. The active region 5 includes an active layer which is a compound semiconductor layer having a multiple quantum well structure.
In particularIn this embodiment, the structure of the device is designed according to the VCSEL theory, a Metal Organic Chemical Vapor Deposition (MOCVD) technique is used to prepare a VCSEL epitaxial wafer, and then a VCSEL device is prepared based on the epitaxial wafer, where: the substrate 1 is a GaAs wafer; the buffer layer 3 is N-doped AlGaAs; the lower distributed Bragg reflector 4 is an N-type Distributed Bragg Reflector (DBR) made of Al0.9Ga0.1As/Al0.12Ga0.88As is laminated; the active region 5 is composed of five pairs of InyGa(1-y)As/AlxGa(1-x)As quantum well and In of graded compositionyGa1-yAs or AlxGa(1-x)An As spacer layer; the oxidation limiting layer 6 is made of Al with a thickness of 30nm0.98Ga0.02As, formation of Al by lateral oxidation2O3Layer, the insulating properties are good; the oxidation-limiting layer 6 is Al0.9Ga0.1As/Al0.12Ga0.88A P-type DBR formed by laminating As, and forming an upper distributed Bragg reflector (7); the lower electrode 2 is made of Ni-Cr-Ge alloy; the upper electrode 8 is made of Ti-Pt-Au alloy.
The preparation process of the VCSEL is as follows: carrying out mesa etching on a VCSEL epitaxial wafer prepared by epitaxial growth by adopting an inductively coupled plasma etching (ICP) device, carrying out water vapor oxidation on the VCSEL epitaxial wafer after the etching is finished, then passivating the oxidized VCSEL epitaxial wafer by adopting a Plasma Enhanced Chemical Vapor Deposition (PECVD) technology, then preparing a lower electrode 2 of a device by adopting a magnetron sputtering process, thinning and polishing the N surface and preparing an upper electrode 8, and finally carrying out annealing treatment to enable the electrodes to form good ohmic contact so as to obtain the VCSEL chip.
The VCSEL inevitably generates heat during continuous operation. The generation of heat consumes a large amount of electric power, and the electric-to-optical conversion efficiency of a VCSEL is typically less than 50%. The heat generated at the same time may cause the temperature of the device to rise, and further, the operating characteristics of the device may be deteriorated or even the device may not operate.
Thermal resistance is generally used to describe the thermal characteristics of the VCSEL, the heat generating part of the VCSEL device is mainly the active region, and the temperature variation Δ T of the region depends on the thermal resistance R of the whole devicethAnd the generated thermal power PHeatAs shown in formula (1))：
ΔT＝RthPHeat (1)
Generated thermal power PHeatEqual to the total electric power UI minus the emitted optical power POutExpressed by formula (2):
PHeat＝UI-POut (2)
assuming that the temperature of the active region of the VCSEL is uniform, the thermal resistance R of the devicethCan be represented by formula (3):
where ξ is the thermal conductivity and d is the oxidation pore size of the oxidation limiting layer. It is known that under the condition of constant current density, the larger the limiting oxide aperture is, the larger the temperature change of the active region is, which means that, in a certain range, the smaller the limiting oxide aperture is, the larger the thermal resistance is, and the larger the operating current density is, the larger the junction temperature of the device is.
The oxidation limiting layer 6 can play a role in photoelectric limitation, and after the thermal characteristics of single-tube devices with different oxidation apertures are researched, the smaller the oxidation aperture is, the larger the thermal resistance of the device is, and the thermal resistance can be reduced by increasing the oxidation aperture.
In order to realize the oxide apertures with different shapes and sizes, the VCSEL devices with different shapes and sizes are designed, and a series of VCSEL devices with different oxide aperture shapes and sizes are prepared by using a water vapor oxidation process. The results show that under the same oxidation conditions, the oxidation aperture varies when the mesa etching structure is different (i.e. the VCSEL structure design is different).
The results of the laser spectrum tests at different temperatures show that the laser peak of the device is in a linear relationship with the temperature rise, the fundamental reason for the red shift of the spectrum is that the temperature rise causes the gain change, and the cavity mode gain spectrum and the quantum well gain spectrum are both red-shifted. The gain peak of the quantum well cannot determine the lasing wavelength of the VCSEL, which is determined by the cavity mode, and as the temperature increases, the effective optical thicknesses of the active region and the DBR of the device increase, and thus the corresponding optical wavelengths increase.
In an embodiment, a driving circuit to drive an array includes:
the charging control module is used for controlling the charging of the circuit;
the energy storage module is used for storing electric energy;
the discharge control module is used for controlling the energy storage module to discharge;
and the main control circuit module is used for outputting a charging control signal and a discharging control signal.
The specific working mode is as follows: the circuit controlling the anode is first charged and then the circuit controlling the cathode is used to achieve instantaneous discharge. The charging control module comprises a plurality of input ends corresponding to the lasers, isolating devices of all channels, charging control switches of all channels and output ends, all the components are connected together, the current output of all the channels can be adjusted, different junction temperatures of all the VCSELs are formed, and wavelength tuning is achieved.
Furthermore, each VCSEL can be individually addressed and driven, and the junction temperature of the VCSEL can be further adjusted by changing the input current of the VCSEL, wherein different junction temperatures can bring different lasing wavelengths of the VCSEL, so that the wavelength tuning is formed.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (6)
1. A vertical cavity surface emitting laser array with tunable wavelength is characterized in that inherent thermal resistances of all vertical cavity surface emitting lasers are different, all the vertical cavity surface emitting lasers are connected by adopting a common anode, and cathodes of all the vertical cavity surface emitting lasers are respectively connected with a driving circuit.
2. A wavelength tunable vcsel array according to claim 1, wherein the oxidized aperture of the oxidized confinement layer of each vcsel is different.
3. A wavelength tunable vertical cavity surface emitting laser array according to claim 1, wherein said vertical cavity surface emitting laser comprises:
a substrate (1);
a lower electrode (2) formed on the lower surface of the substrate (1);
a buffer layer (3) formed on the upper surface of the substrate (1);
a lower distributed Bragg reflector (4) formed on the upper surface of the buffer layer (3);
an active region (5) formed on the upper surface of the lower distributed Bragg reflector (4);
an oxidation limiting layer (6) formed on the upper surface of the active region (5);
an upper distributed Bragg reflector (7) formed on the upper surface of the oxide confinement layer (6);
and an upper electrode (8) formed on the upper surface of the upper DBR (7).
4. A wavelength tunable vertical cavity surface emitting laser array according to claim 1, wherein said drive circuit for driving said array comprises:
the charging control module is used for controlling the charging of the circuit;
the energy storage module is used for storing electric energy;
the discharge control module is used for controlling the energy storage module to discharge;
and the main control circuit module is used for outputting a charging control signal and a discharging control signal.
5. A wavelength tunable vcsel array according to claim 3, wherein the lower dbr (4) and the upper dbr (7) are each formed by alternately stacking compound semiconductor layers having different refractive indices.
6. A wavelength tunable vertical cavity surface emitting laser array according to claim 3, wherein the active region (5) comprises an active layer which is a compound semiconductor layer having a multiple quantum well structure.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114300949A (en) * | 2022-01-19 | 2022-04-08 | 深圳市中科光芯半导体科技有限公司 | Vertical cavity surface emitting laser array with tunable wavelength and tuning method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114300949A (en) * | 2022-01-19 | 2022-04-08 | 深圳市中科光芯半导体科技有限公司 | Vertical cavity surface emitting laser array with tunable wavelength and tuning method |
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