An optimized power-on method for a series-parallel tunable laser array

Abstract

The present invention discloses an optimized power supply method for a series-parallel tunable laser array. S1: Grow an integrated thin film resistor on the surface of the series-parallel tunable laser array, or grow a thin film resistor on the thin film circuit of the patch of the series-parallel tunable laser array; S2: Calculate the power supply schemes for each laser, multiplexer, and optical amplifier in the series-parallel tunable laser array that require different single power supplies; S3: By controlling the magnitude of the resistance value of the thin film resistor, achieve the distribution of current in the series-parallel tunable laser array, and power the lasers, multiplexers, and optical amplifiers in the series-parallel tunable laser array with a single power supply. The number of current sources for the series-parallel lasers is significantly reduced, thereby reducing the system complexity for the further application of the series-parallel lasers.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technologies, and particularly relates to an optimized power supply method for a series - parallel tunable laser array. Background Art

[0002] The wavelength of a series - parallel laser can be tuned by selecting the lasing wavelength and controlling the temperature of the laser. In many application fields, such as optical access networks or coherent optical communication networks using wavelength - division multiplexing, a laser array is required to achieve flexible wavelength configuration; in systems such as optical coherence tomography imaging and optical frequency domain reflectometry, a laser array is needed to perform wavelength scanning for related detections; in optically controlled phased - array radars, a laser array is required to generate a series of serial optical pulses of different wavelengths to implement a series - fed optically controlled phased array; in fiber optic sensing systems, a laser array is needed as a light source to generate a broadband multi - wavelength light source for detecting the spatio - temporal behavior of the measured field.

[0003] A series - parallel laser requires an external power supply. Taking 4 lasers in series and 4 such series structures in parallel as an example. Generally, an active multiplexer and a semiconductor optical amplifier unit are integrated at the front of the array. When the tunable array is working, both the active multiplexer and the semiconductor optical amplifier need to be injected with current. Only one laser is lit each time during operation, but the lasers in front of the same waveguide need to be injected with small currents respectively to compensate for the intrinsic absorption loss of the material and the waveguide scattering loss. Therefore, each laser requires a current source. For this structure, at least 6 current sources combined with an electrical switch (to achieve the switching of the current source among different waveguides) are required to start the complete power supply.

[0004] However, the increase in the number of current sources means an increase in the area of the surrounding control circuit, an increase in the control complexity of the system, and also an increase in the cost of the system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an optimized power supply method for a series - parallel tunable laser array aiming at the deficiencies of the above - mentioned prior art. By fabricating resistors on the surface of the laser or on the laser carrier, single - power - supply is achieved, greatly reducing the number of power supplies for the lasers, thereby promoting the related applications of series - parallel lasers.

[0006] To achieve the above - mentioned technical purpose, the technical solution adopted by the present invention is as follows:

[0007] An optimized power supply method for a series - parallel tunable laser array, comprising:

[0008] S1. Growing an integrated thin - film resistor on the surface of the series - parallel tunable laser array, or growing a thin - film resistor on the thin - film circuit where the series - parallel tunable laser array is patched;

[0009] S2. Calculate the power supply schemes for each laser, wavelength multiplexer, and optical amplifier that require different single power supplies in the series-parallel tunable laser array;

[0010] S3. By controlling the resistance value of the thin-film resistor, achieve the distribution of current in the series-parallel tunable laser array, and power on the lasers, wavelength multiplexer, and optical amplifier in the series-parallel tunable laser array using a single power supply.

[0011] To optimize the above technical solutions, the specific measures taken also include:

[0012] The resistor in the above S1 is connected between each laser.

[0013] In the above S1, an integrated titanium-platinum thin-film resistor is grown on the surface of the series-parallel tunable laser array and connected to the corresponding laser electrodes;

[0014] Or a tantalum nitride thin-film resistor is grown on the thin-film circuit of the series-parallel tunable laser array patch and connected to the corresponding laser electrodes.

[0015] In the above S2, after equivalent the laser as a diode-resistor series model through Kirchhoff's law, superposition law, and equivalent law, calculate the power supply scheme.

[0016] In the above S3, when powering on, inject lasing current into the lasing lasers, and inject transparent current into the remaining lasers to compensate for the intrinsic absorption loss of the material and the scattering loss of the waveguide.

[0017] The present invention has the following beneficial effects:

[0018] Through relevant analysis of the power-on scheme, grow thin-film resistors on the surface of the laser and the surface of the laser thin-film circuit carrier, so as to supply power with a single power supply. Through current distribution, complete the injection of different values of current into each part. Greatly reduce the number of current sources of the series-parallel lasers, thus reducing the system complexity for the further application of the series-parallel lasers. At the same time, the present invention can also be used in other multi-power semiconductor power supply situations. Description of the Drawings

[0019] Figure 1 It is the optimized power-on schematic diagram of the series-parallel tunable laser array of the present invention;

[0020] Figure 2 It is the scheme of growing an integrated thin-film resistor on the surface of the series-parallel tunable laser array of the present invention;

[0021] Figure 3 It is the scheme of growing a thin-film resistor on the thin-film circuit of the series-parallel tunable laser array patch of the present invention;

[0022] Figure 4Power-on test results for three power supplies in the embodiments of the present invention;

[0023] Figure 5 Thin film resistor test results on the chip in the embodiments of the present invention;

[0024] Figure 6 Thin film resistor test results on the heat sink in the embodiments of the present invention;

[0025] Figure 7 Flow chart of the optimized power-on method for the series-parallel tunable laser array of the present invention. Detailed implementation manners

[0026] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] See Figure 7 , an optimized power-on method for a series-parallel tunable laser array, including:

[0028] S1. Grow an integrated thin film resistor on the surface of the series-parallel tunable laser array, or grow a thin film resistor on the thin film circuit (carrier) where the series-parallel tunable laser array is patched;

[0029] That is, it includes the scheme of growing a thin film resistor on the series laser chip and the scheme of growing a resistor on the series laser carrier: introducing a resistor during the growth of the laser or introducing a current distribution resistor when the laser is patched on the carrier;

[0030] Grow an integrated titanium-platinum thin film resistor on the surface of the series-parallel tunable laser array and connect it to the corresponding laser electrode;

[0031] Or grow a tantalum nitride thin film resistor on the thin film circuit (carrier) where the series-parallel tunable laser array is patched and connect it to the corresponding laser electrode.

[0032] That is, the resistor forms a titanium-platinum thin film resistor with the primary electrode process step during the growth of the laser and is connected to the corresponding laser electrode; or a tantalum nitride thin film resistor is grown on the laser carrier and connected to the corresponding laser electrode.

[0033] S2. Calculate the power supply schemes for each laser, multiplexer, monolithic integrated optical amplifier, etc. that require different single power supplies in the series-parallel tunable laser array through the current distribution formula;

[0034] After equivalent the laser to a diode-resistor series model through Kirchhoff's law, superposition law, and equivalent law, calculate the current distribution formula.

[0035] Both the diode and the resistor are ideal models.

[0036] S3. By controlling the resistance value of the thin-film resistor, the distribution of current in the series-parallel tunable laser array is realized, and a single power supply is used to power the lasers, multiplexers, and optical amplifiers in the series-parallel tunable laser array.

[0037] When powering on, it is necessary to consider injecting lasing current mainly into the lasing lasers, and injecting small current (transparent current) into the remaining lasers to compensate for the intrinsic absorption loss of the material and the scattering loss of the waveguide.

[0038] The series-parallel tunable laser array often includes a laser array, an active multiplexer, and a semiconductor optical amplifier. Corresponding currents need to be injected during operation. Through the resistor current distribution mechanism of the present invention, a single power supply can be used to power the lasers, multiplexers, and optical amplifier units in the series-parallel tunable laser array, greatly reducing the number of current sources in the series-parallel tunable laser array, thereby reducing the system complexity for the further application of the series-parallel tunable laser array. At the same time, the present invention can also be used in other multi-power semiconductor power supply situations.

[0039] The principle description, embodiments, and application test results are as follows:

[0040] The equivalent model of the series-parallel tunable laser array obtained by the method of the present invention is as Figure 1 shown. In the equivalent model of the series-parallel tunable laser array as Figure 1 shown, the laser is equivalent to a combination of a diode and a resistor, and the lasers are connected by resistors.

[0041] Figure 1 In [figure], 101, 012, 103, and 104 are ideal equivalent diodes of the lasers. The four diodes have the same parameters and have a turn-on voltage V; 201, 202, 203, and 204 are equivalent resistors of the lasers, and the four resistors have the same resistance value of R; 301, 302, 303, and 304 are thin-film resistors introduced by the laser array, and their resistance values are controlled by controlling the length and width of the thin-film resistor, and the resistance values are R1, R2, R3, and R4 respectively.

[0042] Assume that the lasers adopt a common cathode structure, which is the connection point of 401. At the same time, 402, 403, 404, and 405 are the external current source electrical injection points.

[0043] When the current distribution ratio is X, according to Kirchhoff's law, superposition law, and equivalent law, the following relevant formulas can be obtained:

[0044] XR - XR1 = R2 + R = R3 + R = R4 + R

[0045] XR - XR2 = R1 + R = R3 + R = R4 + R

[0046] XR - XR3 = R1 + R = R2 + R = R4 + R

[0047] XR - XR4 = R1 + R = R2 + R = R3 + R

[0048] (X - 1)R = (X + 1)R1 = (X + 1)R2 = (X + 1)R3 = (X + 1)R4

[0049] After estimating the turn - on voltage of the ideal diode and the resistance value of the laser equivalent resistance, the magnitude of the current - dividing resistance value to be introduced can be deduced.

[0050] (1) The steps for growing an integrated thin - film resistor on the surface of a series - parallel tunable laser array are as follows:

[0051] As Figure 2 shown, a resistor is introduced during the growth process of the laser material. Taking the distributed feedback laser as an example, its epitaxial material is grown by two - step metal - organic chemical vapor deposition (MOCVD). First, an n - InP buffer layer, an n - InAlGaAs lower optical confinement layer, an InAlGaAs multiple quantum well (MQW) structure, a p - InGaAsP upper optical confinement layer, and a p - InGaAsP grating layer are continuously grown on an InP substrate. Using the traditional grating method, a sampled grating is fabricated in the form of a combination of holographic exposure and conventional exposure.

[0052] Then, photolithography and subsequent etching processes are carried out, and then the growth of the p - InP cladding layer and the p - InGaAs contact layer is carried out.

[0053] A ridge waveguide structure is etched using a process combining wet and dry methods, and good electrical isolation is formed between different power - supply units by removing the heavily doped region above the ridge waveguide.

[0054] An insulating layer is grown on the chip surface. The insulating layer is removed directly above the ridge waveguide where the injection current passes, and an electrode material is covered. At the position of the adjacent insulating layer, a titanium - platinum resistor is grown. By controlling the thickness, length, and width of the titanium - platinum thin - film resistor, its resistance value can be controlled.

[0055] (2) The steps for growing a thin - film resistor on the thin - film circuit (carrier) of a series - parallel tunable laser array patch are as follows:

[0056] As Figure 3 shown, the laser needs to be patched on the thin - film circuit carrier during use. Taking the AlN ceramic dielectric as an example, first, the AlN carrier is cleaned and thermally baked, and then tantalum nitride resistors are sputter - grown. By controlling the length, width, and height of the tantalum nitride, the resistance value of the tantalum nitride resistor can be controlled.

[0057] During the sputtering process of tantalum nitride resistors, negative nitrogen pressure is introduced. At the same time, a tantalum pentoxide passivation layer will be formed on the surface of the resistor after thermal oxidation to protect its stability. After sputtering the tantalum nitride resistor, Au electrodes are sputtered and grown at both ends of the resistor. The two electrodes are connected by the resistor, and subsequent photolithography, development, and etching are used to realize the design of the resistor and electrode shapes.

[0058] It should be noted that the method of introducing resistors in the present invention is only one applied to distributed feedback semiconductor laser arrays. However, there are many ways to choose the growth of resistors, and their final models can be normalized to the aforementioned design.

[0059] In the embodiment of the present invention, taking three lasers connected in series as an example, the operating current of the operating laser is 80 mA. The other lasers need to add a small current to compensate for the intrinsic loss of the material and the scattering loss of the waveguide. This small current is about 20 mA (transparent current). According to the above analysis and calculation method, the corresponding resistor values need to be grown between the lasers. A current distribution of approximately 1:4 is achieved. When the series-parallel tunable laser array works, the main current is injected into the operating laser, and only the transparent current (compensating for the loss of the laser during the transmission of other lasers) needs to be injected into the other lasers.

[0060] According to the proportional current designed by the present invention, a total current of 120 mA needs to be injected to achieve the corresponding situation.

[0061] In the embodiment of the present invention, corresponding test and verification experiments are carried out in the form of growing integrated thin-film resistors on the surface of the series-parallel tunable laser array.

[0062] As Figure 4 It can be seen that each laser in the series-parallel tunable laser array can lasing at the designed wavelength. Since the current of each laser during operation cannot be directly detected, the working condition of the laser is judged from the laser spectrogram. As Figure 5 shown, when the laser operates in three channels, it lases in single mode, and the side mode suppression ratio reaches 40 dB.

[0063] At the same time, relevant comparisons are also made with multi-power supply. Lasers produced on the same batch of wafers adopt the multi-power supply form. Three laser series units require three different power supplies. Its spectrogram is similar to that of single-power supply, the main mode lasing power is similar, and the side mode suppression ratio is similar.

[0064] It can be judged from this that by growing integrated thin-film resistors on the surface of the series-parallel tunable laser array, an optimized power supply method based on the series-parallel tunable laser array is realized, reducing the number of laser power supplies, but still having a similar working effect to multi-power lasers.

[0065] Another embodiment of the present invention has carried out relevant test verification experiments. Three lasers are patched in series on a thin film carrier. The operating current of the lasers is 80 mA. The remaining lasers need to add a small current to compensate for the intrinsic loss of the material and the scattering loss of the waveguide. This small current is about 20 mA (transparent current). According to the above analysis and calculation method, the corresponding resistance values need to be grown between the lasers. Subsequently, a tantalum nitride material thin film is grown on the carrier, and then it is connected through electrodes, as Figure 6 shown.

[0066] At the same time, relevant comparisons are also made with multi-power supply. Lasers produced on the same batch of wafers adopt the multi-power supply form. Three laser series units require three different power supplies. Its spectrogram is similar to that of single-power supply, the main mode lasing power is similar, and the side mode suppression ratio is similar.

[0067] It can be judged that by growing tantalum nitride resistors on the surface of the carrier when patching the lasers, an optimized power supply method for the series-parallel tunable laser array is realized, reducing the number of laser power supplies, but still having a similar working effect to multi-power lasers.

[0068] It should be noted that the embodiment of the present invention is only a situation applied to the distributed feedback semiconductor laser array. However, the applicable scope of this optimized power supply method based on the series-parallel tunable laser array is far more than this. As described in the present invention, resistors can be introduced either during the laser design process or on the heat sink carrier where the lasers are located, thereby realizing an optimized power supply scheme.

[0069] The above is only the preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. An optimized power - on method for a series - parallel tunable laser array, characterized in that, Including: S1. Growing an integrated thin-film resistor on the surface of a series-parallel tunable laser array, or growing a thin-film resistor on the thin-film circuit of the series-parallel tunable laser array patch; the resistors are connected between the respective lasers; the grown thin-film resistors are connected to the corresponding laser electrodes; S2. Calculating the power supply schemes for the respective lasers, multiplexers, and optical amplifiers in the series-parallel tunable laser array that require different single power supplies; S3. By controlling the magnitude of the thin-film resistor value, realizing the distribution of current in the series-parallel tunable laser array, and powering the lasers, multiplexers, and optical amplifiers in the series-parallel tunable laser array using a single power supply.

2. The optimized power-on method for a series-parallel tunable laser array according to claim 1, characterized in that, In S1, an integrated titanium-platinum thin-film resistor is grown on the surface of the series-parallel tunable laser array and connected to the corresponding laser electrodes; or a tantalum nitride thin-film resistor is grown on the thin-film circuit of the series-parallel tunable laser array patch and connected to the corresponding laser electrodes.

3. The optimized power-on method for a series-parallel tunable laser array according to claim 1, characterized in that In S2, after equivalent the lasers to a diode and resistor series model through Kirchhoff's law, superposition law, and equivalent law, the power supply scheme is calculated.

4. The optimized power-on method for a series-parallel tunable laser array according to claim 1, characterized in that, In S3, when powering on, a lasing current is injected into the lasing lasers, and a transparent current is injected into the remaining lasers to compensate for the intrinsic absorption loss of the material and the scattering loss of the waveguide.

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