A high-speed picosecond pulse laser driver circuit based on radio frequency triode

Abstract

The application provides a high-speed picosecond pulse laser driver circuit based on a radio frequency triode, which comprises a signal generator, a high-speed level converter, a radio frequency triode Q2 and a DFB laser, the signal generator generates a narrow pulse signal for driving the laser, the narrow pulse signal is converted into an ECL level by the high-speed level converter, the radio frequency triode Q2 is driven to drive the DFB laser to emit light.The application has the advantages that: compared with a high-speed current source driving chip, the high-speed level converter is more universal, so it has more cost advantages; in addition, the high-speed current source driving chip needs a DAC to additionally provide an output adjusting driving current, and the high-speed level converter does not need it, so it has more cost advantages.

Description

Technical Field

[0001] This invention relates to a driving circuit, and more specifically to a high-speed picosecond pulsed laser driving circuit for a single-photon source for quantum communication. Background Technology

[0002] In semiconductor lasers, direct modulation is generally used to generate optical pulses by modulating a DFB laser using the gain-switching principle. Specifically, a narrow pulse current is used to drive the semiconductor laser from below the threshold current. By adjusting the width and amplitude of the narrow pulse current, only the first peak in the relaxation oscillation process is captured, and the remaining oscillations are suppressed to obtain an ultrashort optical pulse.

[0003] like Figure 1 As shown in the published patent CN201720945107, a high-speed laser driving module for a single-photon source in quantum communication provides a high-speed picosecond pulse laser driving system. This scheme includes a high-speed current source driving chip U1, a transistor Q1, and a laser diode LD. The collector of the transistor Q1 is connected to the negative terminal of the laser diode LD, and the positive terminal of the laser diode LD is connected to the power supply VCC. The current source driving chip U1 converts the externally input narrow pulse voltage signal into a corresponding narrow pulse current signal for output. At the same time, the current signal controls the switching of the transistor Q1, and then controls the switching of the laser diode LD, thereby obtaining high-speed picosecond pulse light.

[0004] In a standard 14-pin butterfly-packaged laser, the positive pin (+) of the light-emitting diode (LD) is typically connected to the housing. Connecting the housing to signal ground effectively shields against external interference and protects the internal laser chip, thermoelectric cooler, and backlight power diode. In the aforementioned patented solution, the positive pin of the LD is connected to the power supply VCC, failing to provide shielding. Furthermore, the butterfly-packaged laser is relatively large, with a significant portion of the housing exposed, which can easily cause short circuits on a circuit board.

[0005] High-speed current source driver chips require an additional DAC channel to set the drive current, used to adjust the static parameters of the transistor, increasing the circuit's configuration options. Simultaneously, the magnitude of the drive current of the high-speed current source driver chip and the transistor's amplification factor H also need to be considered. FE Temperature inevitably affects the laser diode LD drive current, which in turn affects the stability of the laser diode LD output power at high and low temperatures.

[0006] In addition, the existing technology requires a limited number of high-speed current source driver chips with few available models, lacking compatibility and replaceability, and with high cost per unit. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to achieve good shielding of internal components of a high-speed picosecond pulsed laser in a low-cost driving circuit.

[0008] The present invention solves the above-mentioned technical problems through the following technical means: The present invention provides a high-speed picosecond pulse laser driving circuit based on radio frequency transistor, which includes a signal generator, a high-speed level converter, a radio frequency transistor Q2 and a DFB laser. The signal generator generates a narrow pulse signal for driving the laser, which is converted into an ECL level by the high-speed level converter to drive the radio frequency transistor Q2 to drive the DFB laser to emit light.

[0009] As a further optimized technical solution, the output terminal of the signal generator is connected to the input terminal of the high-speed level converter, the output terminal of the high-speed level converter is connected to the base B of the RF transistor Q2, the emitter E of the RF transistor Q2 is connected to the potential VE, and the collector C of the RF transistor Q2 is connected to the DFB laser.

[0010] As a further optimized technical solution, the DFB laser includes a light-emitting laser diode LD, a resistor R20, and an inductor L. One end of the resistor R20 is connected to the collector C of the radio frequency transistor Q2, and the other end of the resistor R20 is connected to one end of the inductor L. The other end of the inductor L is connected to the negative DC terminal DC-. The negative terminal of the light-emitting laser diode LD is connected between the resistor R20 and the inductor L, and the positive terminal LD+ of the light-emitting laser diode LD is grounded.

[0011] As a further optimized technical solution, when the output of the high-speed level converter is low, the RF transistor Q2 is cut off, and the DFB laser does not emit light; when the output of the high-speed level converter is high, the RF transistor Q2 is turned on, and the DFB laser emits light.

[0012] As a further optimized technical solution, resistor R10 is connected between the base B and emitter E of the RF transistor Q2.

[0013] As a further optimized technical solution, the high-speed level converter is powered by a negative power supply, i.e., VCC = 0V, VEE = -3.3V, and the voltage of the potential VE is VCC - 2V = -2V.

[0014] As a further optimized technical solution, a temperature compensation circuit is introduced for the potential VE of the emitter E of the radio frequency transistor Q2.

[0015] As a further optimized technical solution, the temperature compensation circuit includes a follower amplifier OPA1, a non-inverting proportional amplifier OPA2, resistors R30, R40, NTC, R50, R60, R70, and R80. Resistors R30 and R40 are connected in series to form a voltage divider to divide the power supply VEE. The voltage divider node M is connected to the non-inverting input terminal of the follower amplifier OPA1. The inverting input terminal of the follower amplifier OPA1 is connected to the output, forming a follower circuit. The NTC resistor and R60 are connected in parallel and then connected in series with R70 to form a voltage divider to divide the operational amplifier output Vo. The voltage divider node N is connected to the non-inverting input terminal of the non-inverting proportional amplifier OPA2. The inverting input terminal of the operational amplifier is connected to ground by resistor R50 and connected to the output by resistor R80, forming a non-inverting amplifier circuit. The output terminal of the non-inverting proportional amplifier OPA2 is connected to the emitter of the RF transistor Q2.

[0016] As a further optimized technical solution, the radio frequency transistor Q2 is based on SiGe technology and has a cutoff frequency ft>37GHz.

[0017] As a further optimized technical solution, the radio frequency transistor Q2 is assembled into the DFB laser through a die integration method.

[0018] The advantages of this invention are:

[0019] 1. Compared to high-speed current source driver chips, high-speed level converters are more versatile and therefore have a cost advantage. In addition, high-speed current source driver chips require an additional DAC to provide an output to regulate the drive current, while high-speed level converters do not, making them even more cost-effective.

[0020] 2. In this scheme, the LD+ of the light-emitting laser diode is grounded, which can shield the internal components of the laser and avoid short circuits in the laser tube shell due to foreign objects.

[0021] 3. An open-loop compensation circuit is introduced to the emitter potential of the RF transistor to stabilize the laser output power under high and low temperatures. The parameters of the compensation network can be fitted based on the temperature drift characteristics of the circuit components.

[0022] 4. Select RF transistors based on SiGe sixth-generation or higher technology, which have high cutoff frequency, better preserve high and low frequency signals, and reduce signal amplification distortion.

[0023] 5. Radio frequency transistors can be assembled into the butterfly laser through die integration, further reducing parasitic parameters, increasing the circuit's operating frequency, and the drive interface is a standard NECL level, ensuring strong compatibility. Attached Figure Description

[0024] Figure 1This is a schematic diagram of the high-speed drive module circuit for a laser from an existing quantum communication single-photon source.

[0025] Figure 2 This is a schematic diagram of the high-speed picosecond pulse laser driving circuit based on an RF transistor according to an embodiment of the present invention;

[0026] Figure 3 This is a temperature compensation circuit diagram for potential VE in an embodiment of the present invention;

[0027] Figure 4 The present invention provides a comparison of laser output spectra at different temperatures before and after the introduction of the compensation circuit in this embodiment. Figure 4 a represents the spectrum before compensation. Figure 4 b represents the spectrum after compensation. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Figure 2 This is a schematic diagram of a high-speed picosecond pulsed laser driving circuit based on an RF transistor, according to an embodiment of the present invention. The high-speed picosecond pulsed laser driving circuit based on an RF transistor includes a signal generator, a high-speed level converter, an RF transistor Q2, and a DFB laser. The high-speed level converter is an ECL (Emitter-Couple Logic) level converter.

[0030] The output of the signal generator is connected to the input of the high-speed level converter.

[0031] The output terminal of the high-speed level converter is connected to the base B of the RF transistor Q2. The high-speed level converter is powered by a negative power supply, i.e., VCC = 0V and VEE = -3.3V. The emitter E of the RF transistor Q2 is connected to the potential VE, and the collector C of the RF transistor Q2 is connected to the DFB laser. Resistor R10 is connected between the base B and the emitter E of the RF transistor Q2.

[0032] The DFB laser includes a light-emitting diode (LD), a resistor (R20), and an inductor (L). One end of the resistor (R20) is connected to the collector (C) of the radio frequency transistor (Q2), and the other end of the resistor (R20) is connected to one end of the inductor (L). The other end of the inductor (L) is connected to the negative DC terminal (DC-). The negative terminal of the light-emitting diode (LD) is connected between the resistor (R20) and the inductor (L), and the positive terminal (LD+) of the light-emitting diode (LD) is grounded.

[0033] A signal generator produces a narrow pulse signal to drive the laser, which is converted into an ECL level by a high-speed level converter to drive the RF transistor Q2, thereby driving the DFB laser to emit light. The output of the high-speed level converter is connected to the base of transistor Q2 and then to the emitter of transistor Q2 through resistor R20. In this embodiment, the high-speed level converter is powered by a negative power supply, i.e., VCC = 0V, VEE = -3.3V. Resistor R20 is selected as a 50-ohm resistor, and the voltage of VE is VCC - 2V = -2V. Typical values ​​of the high-speed level converter output are: high level VOH = VCC - 1V = -1V, low level VOL = VCC - 1.8V = -1.8V. When the high-speed level converter output is low, the RF transistor Q2 is cut off, and the LED does not emit light; when the high-speed level converter output is high, the RF transistor Q2 is turned on, and the LED emits light. The drive signal output by the high-speed level converter controls the RF transistor Q2.

[0034] On the other hand, due to the amplification factor H of the transistor FE The unavoidable influence of high and low temperatures causes changes in the drive current of the DFB laser, ultimately affecting the stability of its output power under these conditions. By carefully fitting the temperature drift characteristics of the laser drive current under high and low temperatures, a temperature compensation circuit was introduced to the emitter potential VE of the RF transistor Q2, thereby stabilizing the drive current of the DFB laser under these conditions and ensuring the stability of its output power.

[0035] like Figure 3As shown, the temperature compensation circuit for potential VE includes a follower amplifier OPA1, a non-inverting proportional amplifier OPA2, resistors R30, R40, NTC, R50, R60, R70, and R80. Resistors R30 and R40 are connected in series to form a voltage divider for the power supply VEE. The voltage divider node M is connected to the non-inverting input of follower amplifier OPA1. The inverting input of follower amplifier OPA1 is connected to the output, forming a follower circuit. Resistor NTC and resistor R60 are connected in parallel and then in series with resistor R70 to form a voltage divider for the output Vo of follower amplifier OPA1. The voltage divider node N is connected to the non-inverting input of non-inverting proportional amplifier OPA2. The inverting input of non-inverting proportional amplifier OPA2 is connected to ground by resistor R50 and connected to the output by resistor R80, forming a non-inverting amplifier circuit. The output of non-inverting proportional amplifier OPA2 is connected to the emitter of RF transistor Q2.

[0036] The temperature compensation principle is as follows: In the temperature compensation circuit, the output Vo of the follower amplifier OPA1 is VEE * R30 / (R30 + R40), and the output VE of the non-inverting proportional amplifier OPA2 is Vo * R70 / (R70 + R60) / R NTC )*(1+R80 / R50).

[0037] As the temperature increases, the amplification factor H of the RF transistor Q2 decreases. FE With the base current Ib of the RF transistor Q2 remaining constant, the drive current of the DFB laser increases (the collector current of the RF transistor Q2 increases, Ic = H). FE *Ib). After introducing the temperature compensation circuit, as the temperature increases, the resistance of the NTC resistor decreases, the absolute value of the output VE of the non-inverting proportional amplifier OPA2 decreases (reducing the collector supply voltage of the RF transistor Q2), and the driving current of the DFB laser also decreases accordingly. This shows that, with temperature changes, the influence of the compensation circuit on the driving current of the DFB laser is related to the amplification factor H of the RF transistor Q2. FE Conversely, if a suitable compensation coefficient is introduced, the driving current of the DFB laser can be stabilized. Figure 4 The comparison of laser output spectra at different temperatures before and after the introduction of the compensation circuit is presented. Figure 4 a represents the spectrum before compensation. Figure 4 b represents the spectrum after compensation, with different traces representing the spectra at different temperatures. It can be seen that after introducing the compensation circuit, the DFB output spectra have higher overlap at various temperatures, and the output power differences are smaller. Preferably, the RF transistor Q2 is based on SiGe technology, with a cutoff frequency ft > 37GHz, better preserving high and low frequency signals and reducing signal amplification distortion.

[0038] Preferably, the RF transistor Q2 can be assembled into the DFB laser using a die-integrated method, which further reduces parasitic parameters, increases the operating frequency of the circuit, and the drive interface is a standard ECL level, which has strong compatibility.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-speed picosecond pulse laser driving circuit based on a radio frequency transistor, characterized in that: The device includes a signal generator, a high-speed level converter, an RF transistor Q2, and a DFB laser. The signal generator produces a narrow pulse signal to drive the laser, which is converted into an ECL level by the high-speed level converter to drive the RF transistor Q2 to drive the DFB laser to emit light. The DFB laser includes a light-emitting diode LD, a resistor R20, and an inductor L. One end of the resistor R20 is connected to the collector C of the RF transistor Q2, and the other end of the resistor R20 is connected to one end of the inductor L. The other end of the inductor L is connected to the DC negative terminal DC-. The negative terminal of the light-emitting diode LD is connected between the resistor R20 and the inductor L, and the positive terminal LD+ of the light-emitting diode LD is grounded, which can shield the internal components of the laser. The output of the high-speed level converter is connected to the base B of the radio frequency transistor Q2. The emitter E of the radio frequency transistor Q2 is connected to the potential VE. The potential VE introduces a temperature compensation circuit. The temperature compensation circuit includes a follower amplifier OPA1, a non-inverting proportional amplifier OPA2, resistors R30, R40, NTC, R50, R60, R70, and R80. Resistors R30 and R40 are connected in series to form a voltage divider to divide the power supply VEE. The voltage divider node M is connected to the non-inverting input of the follower amplifier OPA1. The inverting input of the follower amplifier OPA1 is connected to the output, forming a follower circuit. The NTC resistor and R60 are connected in parallel and then connected in series with R70 to form a voltage divider to divide the operational amplifier output Vo. The voltage divider node N is connected to the non-inverting input of the non-inverting proportional amplifier OPA2. The inverting input of the operational amplifier is connected to ground by resistor R50 and connected to the output by resistor R80, forming a non-inverting amplifier circuit. The output of the non-inverting proportional amplifier OPA2 is connected to the emitter E of the radio frequency transistor Q2. The output of the follower amplifier OPA1 is Vo = VEE * R30 / (R30 + R40), and the output of the non-inverting proportional amplifier OPA2 is VE = Vo * R70 / (R70 + R60 / / RNTC) * (1 + R80 / R50).

2. The high-speed picosecond pulse laser driving circuit based on an RF transistor as described in claim 1, characterized in that: When the output of the high-speed level converter is low, the RF transistor Q2 is cut off and the DFB laser does not emit light; when the output of the high-speed level converter is high, the RF transistor Q2 is turned on and the DFB laser emits light.

3. The high-speed picosecond pulse laser driving circuit based on an RF transistor as described in claim 1, characterized in that: Resistor R10 is connected between the base B and emitter E of the radio frequency transistor Q2.

4. The high-speed picosecond pulse laser driving circuit based on an RF transistor as described in claim 1, characterized in that: The high-speed level converter is powered by a negative power supply, i.e., VCC=0V, VEE=-3.3V, and the voltage of the potential VE is VCC-2V=-2V.

5. The high-speed picosecond pulse laser driving circuit based on an RF transistor as described in claim 1, characterized in that: The radio frequency transistor Q2 is based on SiGe technology and has a cutoff frequency ft>37GHz.

6. The high-speed picosecond pulse laser driving circuit based on an RF transistor as described in claim 1, characterized in that: The radio frequency transistor Q2 is assembled into the DFB laser using a die-in integration method.

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