JP4432459B2 - Semiconductor laser diode driving method and light emitting device - Google Patents

Description

  The present invention relates to a semiconductor laser diode driving method and a light-emitting device, and particularly preferably relates to high-speed and high-frequency pulse driving of a nitride semiconductor laser diode.

  In conventional semiconductor laser driving, a driving method using only a pulse current corresponding to an input signal as a driving current is known (see FIG. 2A). In this method, a rectangular pulse current is given to the input signal as a driving current for the semiconductor laser. However, in this case, a pulsation of light output called “relaxation oscillation” is observed (see FIG. 2B) with respect to a sudden drive current fluctuation at the rise of the pulse current (see FIG. 2B). Due to fluctuations in the emission spectrum, for example, when used in an optical communication device, it causes a malfunction such as a communication error at the time of transmission / reception, leading to a decrease in communication reliability.

  In order to reduce this relaxation oscillation, the semiconductor laser is provided with a high-frequency bypass circuit composed of, for example, a resistor and a capacitor, or the semiconductor laser is provided with an additional circuit for connecting in parallel a transmission line whose end is opened via a matching resistor. In addition, a drive circuit that absorbs / releases a sudden drive current fluctuation at the time of rising or falling of a rectangular pulse driving part to relieve it in a staircase pattern (Japanese Patent Laid-Open No. 64-9676), Measures have been taken to provide a resonance part having a resonant frequency to be tuned in parallel with the light emitting element (Japanese Patent Laid-Open No. 53-8484). Further, the bias current starts to flow a minute time Δt earlier than the flow of the pulse current corresponding to the input signal, the bias current flows to the end of the flow of the pulse current, and the sum of the bias current and the pulse current is supplied as the drive current. As described above, driving for the purpose of reducing the emission delay and keeping the extinction ratio large by driving a semiconductor laser is known (Japanese Patent Laid-Open No. 9-83050).

  Furthermore, as a semiconductor laser driving method for high-speed communication, in the pulse driving as described in the pamphlet of WO 01/11740, a second bias that rises somewhat earlier than the rising of the pulse driving current is supplied to the semiconductor laser diode. A semiconductor laser driving circuit and a driving method capable of transmitting burst data at high speed and reliably are known. In this method, a first bias current is supplied to the semiconductor laser at least when data is not emitted, and a second bias current is supplied immediately before the data is issued to prepare for burst data emission. The laser is driven in the spontaneous emission region. When a predetermined time elapses after the supply of the second bias current starts, a pulse current is supplied to the semiconductor laser, and a burst optical signal corresponding to the data signal is output from the semiconductor laser. The optical output waveform of the semiconductor laser rises from the leading waveform of burst data without deterioration due to oscillation delay or the like, and high-speed burst data can be emitted.

  Further, as a driving method capable of reducing the temperature rise of a high-power semiconductor laser and extending its lifetime, as disclosed in Japanese Patent Application Laid-Open No. 7-38184, the semiconductor laser diode is operated immediately before applying a pulse current for driving the laser. By applying a pulse bias current having a current value less than the threshold value, it is possible to reduce the rise time of the high gate pulse current of the laser driving transistor to 1 μsec or less required for the optical thyristor firing, and a semiconductor with a bias current. It is known to suppress the temperature increase of the laser active layer. It is described that the semiconductor laser gives a bias to the drive circuit before obtaining the second pulse current from the drive circuit, so that the rise time of the second pulse current is shortened and the semiconductor laser is driven at high speed. It is what.

International Publication No. 01/11740 Pamphlet JP 7-38184 A JP-A-64-48481 JP 2000-138415 A

When high-speed data modulation is performed on a semiconductor laser based on an input signal, for example, when a pulse-shaped rectangular wave drive current is supplied, a transient phenomenon occurs due to a sudden change in the drive current, and so-called relaxation oscillation occurs.
This relaxation oscillation increases corresponding to the magnitude of the drive current and the current rising speed, and causes a communication error during transmission / reception when used in an optical communication device, for example, due to fluctuations in emission intensity or emission spectrum. There are drawbacks. Further, even if the relaxation oscillation can be reduced by the method described in the prior art, there is a problem that the rise and fall of the light output are slowed this time. This is because the rise of the drive current is delayed according to the time constant of the high frequency bypass circuit, etc., which causes errors such as communication, and when the rise of the drive current is moderate to suppress relaxation vibration. It was a hindrance to high frequency driving.

  Furthermore, as shown in FIG. 5, there is a phenomenon that “rounding” is considered to occur due to current reflection of the driving current at the fall of the light emission output during pulse driving, and the presence of this “rounding” causes particularly high-speed and high-frequency modulation driving. The problem of being disturbed was found. In other words, in order to realize high-speed and high-frequency modulation driving, quick rise and fall response characteristics corresponding to the drive current are required, but since this “round” exists, the optical output Will fall behind the drive current.

  As a result, the time interval until the start of rising of the light output by the next drive current cannot be shortened because it is performed after the light output is sufficiently lowered and extinguished (or dimmed), and there is a limit. Furthermore, if the next drive current is supplied in a state where the light output is not sufficiently lowered due to “rounding” and the light output is raised to a high light emission state, the extinction ratio cannot be maintained sufficiently, and the drive current is not maintained. Regardless of the supply of light, the light emission state is always high, that is, it cannot cope with high-speed and high-frequency driving.

  In addition, since the nitride semiconductor laser has a large differential resistance value, there is also a problem that a delay is likely to occur at the rise and fall of the light emission output during pulse driving. In high-speed / high-frequency modulation driving of a semiconductor laser diode, the recording density and the amount of information to be written can be increased as the modulation speed increases, but if high-speed / high-frequency modulation is hindered, for example, a nitride-based semiconductor laser is used. This becomes a limit when increasing the recording density on the storage medium, and causes a problem.

  The present invention obtains an optical output waveform with reduced light emission delay and dimming delay based on the pulse waveform of the drive current, reduces relaxation oscillation, and reduces rounding at the time of falling optical output, thereby overshooting the optical output. Drives a semiconductor laser that prevents the occurrence of undershoot and undershoot, is stable without reducing the extinction ratio, has few errors such as communication and writing, and has a fast operation speed and high-speed / high-frequency modulation capable of high-speed and high-frequency modulation. There is to do.

  That is, an object of the present invention is to solve the known problems in conventional red semiconductor lasers and the like, such as reducing the influence of relaxation oscillation of the semiconductor laser, and at the same time, a low power consumption semiconductor capable of high speed and high frequency modulation with improved falling characteristics. A laser driving method and a light emitting device are provided.

  Furthermore, in the driving method in which a pre-bias less than the threshold current in a spontaneous emission state is applied, relaxation oscillation occurs when a pulse signal is applied, and a problem arises in speeding up the rise of pulse emission. That is, in the driving method described in the pamphlet of International Publication No. 01/11740 and Japanese Patent Laid-Open No. 7-38184, transmission of burst data is performed because the carrier density in the semiconductor laser diode reaches near the threshold carrier density due to pre-bias. Although it is described that the oscillation delay is reduced at the time, the oscillation delay still remains because the laser oscillation starts after the burst data is input to the semiconductor laser as the drive current greater than the threshold current At the same time, there is a problem that relaxation oscillation occurs during laser oscillation due to burst data input.

  In the present invention, the quenching delay of the semiconductor laser diode is reduced, and the response of the semiconductor laser diode when applying a pulse data drive current is further improved compared to the conventional case, that is, the light output rise time is greatly shortened and relaxed. The object is to obtain a practical pulsed light output waveform that minimizes the influence of vibration and prevents overshoot and undershoot of the light output.

In order to solve the above-described problems, the present invention is a semiconductor laser diode driving method for causing a semiconductor laser diode to emit light via a driving circuit, and a first driving current is applied from the driving circuit to the semiconductor laser diode. A first step corresponding to the first drive current, and a second step of applying a second drive current from the drive circuit to the semiconductor laser diode following the first drive current. The light output and the second light output corresponding to the second drive current are superimposed and output as a one-pulse light output. From the maximum value in the relaxation oscillation of the first light output, the second light output is The laser diode driving method is characterized in that the laser diode rises so as to be larger than the peak value of the relaxation oscillation.

  According to the present invention, a pulsed light output waveform in which the rise time at the rise of pulse emission of a laser diode is greatly shortened, there is no overshoot or undershoot of the light output, and the influence of relaxation oscillation is reduced to a negligible level. Since this can be realized, high-reliability high-speed / high-frequency driving is possible.

The present invention is the semiconductor laser diode driving method in which the second light output rises from the maximum value of the first light output. As a result, there is a degree of freedom in the rise base of the second light output, so that the rise time is greatly shortened at the time of the pulse emission rise of the laser diode and there is a degree of freedom in the design of the light output waveform and the relaxation oscillation is reduced. Since the rising waveform of the optical output reduced to such an extent that the influence can be ignored can be realized, high-reliability high-speed / high-frequency driving is possible. Note that the “maximum value” in this specification is a value at which the differential value is substantially 0, and does not necessarily indicate the maximum value.

The present invention is the laser diode driving method in which the second light output rises from the maximum value of the first light output. By this invention, it is possible to realize the rising waveform of the optical output that is shortened to the maximum in the present invention and the influence of the relaxation oscillation is negligible while the rising time at the time of the pulse emission rising of the laser diode is minimized. High-reliability high-speed / high-frequency driving is possible.

The present invention is a laser diode driving method in which a current value of a first driving current is smaller than a current value of a second driving current. This makes it possible to realize a light output waveform that greatly reduces the rise time at the time of pulse emission rise of the semiconductor laser diode and can be ignored to the extent that the influence of relaxation oscillation can be ignored, enabling high-speed and high-frequency driving with high reliability. It becomes.

The present invention is a laser diode driving method for supplying a bias current superimposed on a first driving current and a second driving current.

The present invention is a laser diode driving method in which a supply time of a first drive current and a supply time of a second drive current are supply times independent of each other. As a result, the occurrence of overshoot of the optical output is suppressed.

The present invention is a light emitting device for a semiconductor laser diode comprising a semiconductor laser diode and a drive circuit for driving the semiconductor laser diode, wherein the light emitting device for the semiconductor laser diode is driven first from the drive circuit to the semiconductor laser diode. A first current applying means for applying a current; a second current applying means for applying a second drive current from the drive circuit to the semiconductor laser diode following the first drive current; and a first drive current Storage means for storing desired data output as a one-pulse light output by superimposing a corresponding first light output and a second light output corresponding to the second drive current, laser diode from the maximum value in the relaxation oscillation of the optical output, the second light output, characterized in that rises larger than the peak value of the relaxation oscillation of It is a light-emitting device.

  By this invention, the rise time at the time of pulse emission rise of the laser diode is greatly shortened and the influence of relaxation oscillation is reduced to a negligible level, and an optical output waveform without overshoot and undershoot of the optical output can be realized. High-reliability high-speed and high-frequency driving is possible. In addition, since the setting value for reproducing this driving state can be stored in the storage means, the setting value can be read from the storage device when necessary, and the driving based on the setting value can be realized, so the setting is not necessary every time and is reproduced. A light-emitting device capable of realizing a plurality of pulse emission related to the present invention, such as a repetitive pulse, with a simple circuit with good characteristics.

The present invention is the laser diode light emitting device in which the second light output rises from the maximum value of the first light output. As a result, there is a degree of freedom in the rise base of the second light output, so that the rise time is greatly shortened at the time of the pulse emission rise of the laser diode and there is a degree of freedom in the design of the light output waveform and the relaxation oscillation is reduced. Since the optical output rising waveform can be realized so that the influence can be ignored, the high-speed and high-frequency driving with high reliability can be realized.

The present invention is the laser diode light emitting device in which the second light output rises from the maximum value of the first light output. According to the present invention, it is possible to realize a rising waveform of the optical output in which the rise time at the time of the pulse emission rise of the laser diode is reduced to the maximum in the present invention and reduced to such an extent that the influence of relaxation oscillation can be ignored. High-reliability high-speed / high-frequency driving is possible.

The present invention is a laser diode light emitting device in which the current value of the first drive current is smaller than the current value of the second drive current. As a result, the rise time at the rise of the pulse emission of the laser diode is greatly shortened and the rise waveform of the optical output reduced to such an extent that the influence of relaxation oscillation can be ignored can be realized. It becomes possible.

The present invention is a laser diode light emitting device including a bias current supply circuit that supplies a bias current superimposed on a first drive current and a second drive current.
Furthermore, the present invention is a laser diode light emitting device in which the supply time of the first drive current and the supply time of the second drive current are supply times independent of each other. As a result, the occurrence of overshoot of the optical output is suppressed.

(First drive current)
This is a drive current for pre-driving for triggering the rise of the pulse drive light waveform. The shape of the waveform of the drive current is not limited as long as it is pulsed, such as a rectangular wave, a triangular wave, or a sine wave. It is this pulsed first drive current that is supplied prior to the second drive current that causes pulsed light emission, and this current value may be equal to or greater than the threshold current. If the pulsed first drive current is equal to or greater than the threshold value, the rise of the first optical output corresponding to the first drive current is also preferable, but the first drive current is preferably a laser diode. (Hereinafter also referred to as “LD”) is preferably a driving current that is supplied at a magnitude and a time sufficient to start laser oscillation at the first light output, and further, the first driving current is the first light. A pulse shape having a steep rise that is large enough to generate relaxation oscillation in the output is even more preferable because the rise time of the first light output is extremely short.

  Typically, it is most desirable if the first light output is a current value and supply time at which light emission is observed as one-pulse relaxation oscillation. Specifically, this first drive current is the I− of the semiconductor LD. The first light output becomes the base of the second light output rise by letting the current value corresponding to about 10-20% of the rated light output from 3 mW to 6 mW light output in the L characteristic curve as the set value. This is particularly preferable since a steep rise can be realized. The preferred application time of the first drive current varies depending on the LD frequency response characteristics, but in LDs with good frequency response characteristics, the injection current can be reduced and shorter supply time can be achieved, that is, the time integrated current value can be reduced. In addition, in an LD having poor frequency characteristics, a preferable first light output can be obtained by supplying a longer time or setting a larger current, that is, by increasing a time integration current value. However, if the supply time of the first drive current is short and it is an instantaneous pulse, the optical output as set may not be observed, and it is accurately confirmed whether the current value set and supplied is flowing. There are things you can't do.

  This pulsed first drive current may be temporally separated / independent from the second drive current as shown in FIG. 9, or may partially overlap in time. The rising edge of the first light output corresponding to the pulsed first driving current, preferably the first driving current and the second driving current so that the rising of the second light output starts from the peak value. The supply conditions (for example, the drive current value or the maximum pulse drive current value, the supply time and the relative supply timing, etc.) may be adjusted.

(Second drive current)
As shown in a typical example in FIG. 9, the pulse drive current supplied to the laser diode subsequent to the first drive current which is the preliminary drive current is referred to as a second drive current. Typically, the second driving current is supplied in relation to the first driving current so that the rising edge or peak value of the first light output or the rising edge of the second light output starts from the rising edge. Is adjusted and supplied to the laser diode as a second drive current.

(First light output)
Since the first drive current is supplied above the threshold, the first light output is observed. For example, even if a drive current corresponding to 3 to 6 mW or 10 to 20% of the rated light output is supplied and set on the IL characteristic curve, the light output as designed may not necessarily be observed. The first light output is preferably a light output in which a plurality of relaxation vibration peak values are observed, although only one relaxation vibration is preferably emitted. Typically, a state where one pulse peak having a peak value smaller than the second light output is observed as relaxation oscillation is most preferable.

(Second light output)
The light output originally expected as pulse drive is referred to as second light output, and the drive current is referred to as second drive current. The waveform of the pulse drive current may be a second drive current that can obtain a desired light emission output according to the second light output, which is required such as a sine wave, rectangular wave, triangular wave, sawtooth wave, etc. The shape does not depend on the practice of the present invention.

(Superimposed one-pulse light output)
Typically, the light output shown in FIG. 9 is formed by superimposing the first light output and the second light output into one pulse.

(Rising part, peak part or falling part of the first light output)
Although it is most preferable that the second light output rises from the peak value of the first light output, for example, the peak value of the first relaxation oscillation, it is not necessarily limited to this. Sufficiently fast rise characteristics can be realized even from the second and third relaxation vibration peak portions (maximum values). Further, although the effect is somewhat reduced, the same applies to the rising portion and the falling portion in the vicinity of the peak portion even if it is not the peak portion.

(Desired set value)
The set value is a supply condition, typically a supply time, current value, and first and second relative supply timings of the first drive current, and a desirable first drive current magnitude, supply time, and supply. The set value is adjusted in relation to the second drive current of the pulse drive so as to be the timing and the like. A desirable value of the first drive current is a drive current value corresponding to 3 to 6 mW light output of the semiconductor laser diode or a drive current value corresponding to 10 to 20% light output of the rated light output.

(Memory means)
Any general-purpose storage device such as an IC memory, EEPROM, flash memory, or RAM can be used.

(Light emitting device)
The light emitting device referred to in the present invention includes all devices having a semiconductor laser diode and capable of emitting the semiconductor laser diode. Regardless of whether or not the LD light can be extracted to the outside of the light emitting device, a device that uses LD light emission inside the device or a light emitting device that emits light outside the device may be used. Typically, it may be a communication light emitting device, an optical integrated module, an optical storage writing device (such as a digital video disk writing device), or a minilab using a laser exposure technique. When used as an optical storage writing device, it becomes a writing light source with high speed / high frequency and excellent resolution / SN ratio, and more accurate recording with reduced noise and errors can be expected. In CTP printers for minilabs and newspapers using laser exposure technology for photo development, high-definition, high-density, accurate, and clear printing and printing are possible as light sources for small and light exposure. Is possible. As an optical storage system writing device, it can be applied to CD, DVD, Blu-ray, UDO, MO and the like.

(First drive current supply time and second drive current supply time are independent of each other)
The term “independent” as used herein means that the supply times of the first drive current and the second drive current do not overlap each other in time, that is, do not overlap, that is, the first drive current and the second drive current do not overlap. This means that there is no time during which both drive currents are supplied simultaneously. As shown in FIG. 10, in the drive current generation method of the present invention, in particular, the first drive current is obtained by appropriately shortening the time interval between the independent first drive current and the second drive current. It is desirable to adjust the waveform of the drive current so that the second light output corresponding to the second drive current rises from the emission of the first light output corresponding to.

(input signal)
The input signal referred to in the present invention is a signal for controlling the drive current for controlling the light emission of the semiconductor laser. For example, in the input signal by a digital signal consisting of “0” and “1”, each of the low light emission states (Or / and a non-light emitting state), a pulse current for driving in a high light emitting state can be generated, and this can be set to be superimposed on a bias current and supplied as a driving current for the semiconductor laser. By inputting the input signal at a high speed and at a high frequency, it is possible to set the drive current to be controlled to emit light at a high speed and at a high frequency according to the input signal.

(Drive current)
In order to drive the semiconductor laser, for example, it refers to a current supplied to the semiconductor laser based on an input signal. With this drive current, the semiconductor laser is actually directly controlled in operations such as light emission / quenching. The waveform of the drive current is not particularly limited, such as a sine wave, a rectangular wave, a pulse wave, a triangular wave, and a square wave. Further, each waveform is added or subtracted, or various types such as an adding process and a dividing process are performed. A drive current subjected to arithmetic processing may be used. Alternatively, a current obtained by superimposing various waveform currents on a predetermined bias current can be supplied to the semiconductor laser as a drive current.

  The plurality of stepped rising currents are, for example, a waveform current and a waveform obtained by branching a rectangular pulse waveform current based on an input signal and delaying the waveform current for a predetermined time by a current driving device as shown in FIG. It refers to a drive current having a waveform as shown in FIG. 4 created by synthesizing the processed current. A stepped step can be a waveform created in multiple steps of one or more steps. Further, a bias current can be superimposed on the current, and the current can be supplied as a new drive current to the nitride semiconductor laser.

  In this case, the drive current waveform as shown in FIG. 6 is obtained, but the current value at the B level, which is the first step current value driven at the threshold current or higher at the time of rising in the current waveform of FIG. It is desirable to set the drive current value to such an extent that a light emission output of about 3 to 6 mW can be obtained in the IL characteristic curve of the semiconductor laser diode. In addition, since the light emission corresponding to this current is a short time and a small current value for precise measurement, it is difficult to measure. Therefore, even if 3 to 6 mW light emission cannot be confirmed quantitatively, the IL characteristic curve of the semiconductor laser diode is obtained. It is sufficient to set a current value of 3 to 6 mW. If the B level is too high, relaxation oscillations are likely to occur and become too large when the A bias level is raised to the B level, and the desired optical pulse output (especially the second optical output) may be exceeded. Therefore, it is not preferable.

  Also, in order to keep the extinction ratio large and clearly keep the light emission in two levels of light and dark, when using a semiconductor LD with good frequency response characteristics, the shorter the B level time, the more optimal injection current amount. It is more preferable in setting.

  By adopting the above configuration, while maintaining a stable extinction ratio, it improves the falling edge of the light output without increasing power consumption, enabling high-speed and high-frequency driving, and unprecedented quick light output The rise is realized after reducing the relaxation oscillation, and unnecessary heat generation of the semiconductor laser can be suppressed by the optimum bias current, so that the life of the laser can be extended. The quick rise time of the light output can be set to 1 ns or less in the evaluation at 10% to 90% (measurement time required between 10% values from the peak and the bottom).

  In addition, as a drive current supply device, a bias current supply device and a current supply device that supplies a pulse current such as a rectangular wave can be provided as separate devices. It can also be configured as a device.

(Bias current)
Unlike the driving current of the semiconductor laser, the input is different from the waveform signal current that is supplied according to the input signal “0”, “1”, etc., the rectangular wave, the sine wave, the square wave, the pulse wave, and various arithmetic processes. This is a current that is supplied in superposition with the pulse signal current of the various waveforms supplied according to the signal. If there is no bias current at all, the situation where relaxation oscillation occurs at the rise of the optical output increases, that is, relaxation oscillation is likely to occur, and if the bias current is too large, the “rounding” at the fall of the optical output will increase. This causes an increase in power consumption that does not directly contribute to light emission, unnecessary heat generation, and the like, and promotes element deterioration. It has been found that a suitable value of the bias current is typically less than the threshold current, and the smaller the smaller the “round” at the fall of the light output, the more preferable the light output waveform can be obtained.

  More preferably, it has been confirmed that a more preferable operation can be realized by setting the constantly supplied bias current value to be less than the threshold current value and to a current value larger than “0”. If the bias current value is “0”, each device in the circuit such as a transistor is turned off (non-driving state), and thus the driving current is likely to be affected by disturbances such as noise. That is, it is confirmed that the above bias current value can realize the rapid rise and fall of the light output with reduced relaxation oscillation, and can reduce the influence of “margin” that causes extinction delay / darkening delay. did it.

(Threshold current value)
The threshold current value referred to in the present invention is a current value at which laser oscillation of a semiconductor laser to be driven is generally started as shown in FIG. 3, but more strictly speaking, the drive current vs. optical output of the laser element. It is the current value at the inflection point in the IL characteristic curve showing the relationship.

  According to the present invention, the pulsed light output of the semiconductor laser diode rises very quickly and in a short time, that is, the response speed is very fast with no light emission delay, and the pulsed light output is realized while the relaxation oscillation is reduced. As a result, it is possible to realize semiconductor laser diode drive that supports high-speed and high-frequency drive, as well as pulsed light emission drive that has a particularly excellent S / N ratio and extinction ratio. That is, it is possible to realize pulsed light emission with an extremely fast pulse response speed even though the influence of relaxation oscillation is so small that it can be substantially ignored.

  In addition, according to the present invention, it is possible to perform high-speed and high-frequency driving of a semiconductor laser having a good drive current falling response characteristic and a large optical output rise time and a short optical output rise time.

  Examples are shown below.

Example 1
FIG. 18 shows a schematic configuration diagram of the first embodiment. This configuration uses an Agilent 81130A Pulse Pattern Generator (hereinafter referred to as PPG) (180) as a pulse generator, and the pulse signal input from this PPG (180) is Pulse 1 (181) of the semiconductor laser diode driving IC (187). ), Pulse2 (182). Further, the current inputs from the constant current sources I1 (183), I2 (184), and I3 (185) are connected so as to be input to the IIN1, IIN2, and IIN3 of the semiconductor laser diode driving IC (187), respectively.

  Here, I1 (183) is set as a bias current (1 mA in this embodiment), I2 (184) is set as a first drive current (51 mA in this embodiment), and I3 (185) is during pulse emission. Is set as a current (100 mA in this embodiment) corresponding to the required light emission amount. The semiconductor laser diode (187) is connected to the current output terminal Iout (188) of the drive current output processed by this drive IC (187), and the light emission output waveform of this semiconductor laser diode (187) is Hamamatsu Photonics. Monitoring is performed in real time with SAMPLING-OSCILLOSCOPE OOS-1 (hereinafter referred to as OOS-1) (186).

  Next, an outline description of the operation and procedure will be described below. A pulse signal is output from the PPG (180) to Pulse1 (181) and Pulse2 (182) at the timing described in the operation timing chart of FIG. Adjustment is made so that the bias current Iout1, the first drive current Iout2, and the second drive current Iout3 flow through the constant current sources I1 (183), I2 (184), and I3 (185), respectively. The current values of Iout1, Iout2, and Iout3 are set to a bias current of 1 mA, a first drive current value of 51 mA, and a second drive current value of 100 mA, respectively, as shown in the chart of FIG. ing.

  Subsequently, the drive current Iout (188) of the semiconductor laser diode (187) shown in the time chart of FIG. 19 is adjusted as in the present invention by the procedure described below. First, a driving current that emits light of 3 to 6 mW in the IL characteristic curve of the semiconductor laser diode (187) is determined as a first driving current, and the current value is defined as Iout2 as I2 (184). Set to. In this example, Iout2 was set to 51 mA corresponding to a 4 mW optical output in the IL characteristic curve. At this time, the OOS-1 (186) optical output waveform measurement is performed so that the relaxation time of the emission waveform is output once in the OOS-1 (186) during the supply time for supplying the first drive current for one pulse. The PPG (180) is adjusted while observing the instrument to adjust the pulse signal supply time.

  Further, the second drive current is set to Iout3 so that a drive current that can provide a desired optical output power flows. In this example, in order to obtain a 50 mW optical output in the IL characteristic curve, a driving current of 100 mA was set as Iout3, and I3 (185) was adjusted to the 100 mA current value. After that, the rising edge portion of the second driving current is brought close to the falling edge portion of the first driving current, and the second light output from the vicinity of the peak value of the first light output obtained by the first driving current. The pulse output timing of the PPG (180) is adjusted while observing OOS-1 (186) so as to rise.

  In addition, the second drive current value is suddenly lowered to near 0 mA so that the influence of current reflection due to impedance mismatch between the drive circuit and the LD does not affect the optical output, that is, the extinction delay and the rounding phenomenon are substantially reduced. Can be eliminated. In this embodiment, 1 mA Iout1, that is, 100 mA Iout3 up to the bias current, that is, a driving current that falls at a stroke from the second driving current. With the above procedure, it has become possible to drive the optical output rise / fall time in pulse drive simultaneously to be less than 1 nsec, which has been impossible to realize with conventional nitride semiconductor laser diodes.

  Further, an explanation will be given of the pulse drive operation related to another timing chart shown in FIG. 20 using the same circuit configuration shown in FIG. In the driving current shown in FIG. 20, when the first driving current supply time and the second driving current supply time overlap, that is, the pulse supply times of Pulse 1 (181) and Pulse 2 (182) are shown in FIG. As shown, the drive current is created when they overlap.

  First, PPG (180) outputs to Pulse 1 (181) and Pulse 2 (182) at the timing shown in FIG. Here, it is assumed that the switch SW1 (189) and the switch SW2 (1810) are turned on when a high level voltage is inputted and turned off when a low level voltage is inputted. Next, adjustment is made so that the bias current Iout1, the first drive current Iout2, and the second drive current Iout3 shown in FIG. 20 flow through the constant current sources I1 (183), I2 (184), and I3 (185), respectively. By the above procedure, the drive current Iout (188) of the semiconductor laser diode (1811) shown in FIG. 20 is obtained.

  Thereafter, as a first drive current, Iout2 is set so that a drive current corresponding to an optical output of 3 to 6 mW flows to the semiconductor laser diode (1811) from the IL characteristic curve of the semiconductor laser diode (1811). Adjust I2 to the set value. During the period in which the first drive current is applied, the PPG (180) is adjusted while observing the optical response waveform using an optical waveform measuring instrument such as OOS-1 (186) so that one relaxation oscillation is output. . Further, the second drive current adjusts Iout3 so that a current that provides a desired optical output power flows. Thereafter, the rising edge portion of the second driving current is brought close to the falling edge portion of the first driving current so that the second optical output rises from the vicinity of the peak value of the optical output obtained by the first driving current. Adjust to.

  Further, the second drive current is reduced to about 0 mA at a stretch, so that the influence of current reflection due to impedance mismatch between the drive circuit and the semiconductor LD can be prevented from affecting the optical output. As described above, it has become possible to simultaneously drive the rise and fall times of 1 nsec in pulse driving, which has been impossible to realize with conventional nitride semiconductor laser diodes.

(Example 2)
As a second embodiment, the circuit shown in FIG. 7 is configured and a nitride semiconductor laser is pulse-driven. The drive current supplied to the semiconductor laser with the circuit configuration shown in FIG. 7 can have a drive current waveform equivalent to the drive current waveform shown in FIG. The operation of the circuit will be described below. A bias current (I3) is always supplied by a diode (D3) whose anode side is connected to a current source.

  When the clock 1 (CK1) and the clock 2 (CK2) are input, the transfer gates (T1) and (T2) are turned on according to the timing of the clocks (CK1) and (CK2) when the clock is Hi. Then, the input currents (I1), (I2), and (I3) pass through the diodes (D1), (D2), and (D3) to the anode side of the laser diode (LD) ((I1) + (I2 ) + (I3)) is supplied as the maximum value of the drive current (ID). In this drive current, (I3) is a bias current, and a current value that is increased by one step from the bias current value is a current value of (I1 + I3). This (I1 + I3) current value has a value equal to or greater than the threshold current. It is preferable from the viewpoint of improving the response of the rising light output and suppressing the relaxation oscillation, and more preferably as close to the threshold current value as possible from the viewpoint of power consumption reduction and extinction ratio.

  Further, the bias current (I3) is improved in such a direction that “rounding” is eliminated when the bias current is smaller than the threshold current. However, the smaller the bias current value is, the lower the light output falls. Although the characteristics are further improved and a more suitable light output characteristic can be obtained without “rounding”, (I3) If the current value is “0”, it is not preferable because it is easily affected by disturbances such as noise.

  By driving the nitride-based semiconductor laser by supplying this driving current, it was possible to confirm the light output with reduced “rounding” and relaxation oscillation at the same time as in Example 1.

  Further, the drive circuit according to the embodiment can also be realized in the pulse drive circuit shown in FIG. The operation will be described below. The switch 1SW1 (151) is configured so that the switch 1SW1 (151) is turned on when the signal from the pulse 1PULSE1 (152) is HIGH level (for example, 5V), and is turned off when the signal is LOW level (for example, 0V). The switch 2SW2 (153) has the same configuration.

  A voltage-current conversion circuit comprising an operational amplifier 1OPAMP1 (156), a transistor 1Tr1 (157), and a resistor R2 (158) is generated by flowing a current from the constant current source I1 (154) to the resistor R1 (155). So that current flows through transistor Tr4 (159). Here, since the transistor 4Tr4 (159) and the transistor 5Tr5 (1510) are current mirror circuits, a current having the same magnitude as the current flowing in the transistor 4Tr4 (159) also flows to the transistor 5Tr5 (1510). Specifically, the current also flows to the semiconductor laser diode LD (1511) (referred to as Iout1).

  Here, when a HIGH level voltage signal is input to the pulse 1PULSE1 (152), the switch 1SW1 (151) is closed, and the current corresponding to the current amount of the I2 (1512) becomes the operational amplifier 2OPAMP2 (1513) and the transistor 2Tr2 (1514). , Generated by a voltage-current circuit comprising a resistor R4 (1515). Since this current, that is, Iout2 also flows through the transistor 4Tr4 (159), it is superimposed on the Iout1 and a current of (Iout1 + Iout2) flows to the semiconductor laser diode (1511).

  Next, when a HIGH level voltage is input to the pulse 2PULSE2 (1516), the switch 2 (SW2) is turned OFF, and a current corresponding to the current amount of I3 (1517) is supplied to the operational amplifier OPAMP3 (1518) and the transistor 3Tr3 (1519). ), And is generated by a voltage-current circuit composed of the resistor R6 (1520). Since this current, that is, Iout3 also flows through the transistor 4Tr4 (159), it is superimposed on the above-described (Iout1 + Iout2), and the current of (Iout1 + Iout2 + Iout3) flows to the semiconductor laser diode (1511). If the switch 2SW2 (153) is turned OFF in this state, the current of (Iout1 + Iout2) flows to the semiconductor laser diode (1511). If the switch 1SW1 (151) is turned OFF, the current of Iout1 flows to the semiconductor laser diode (1511).

(Example 3)
An example in which the first drive current and the second drive current are realized by the drive current generation method capable of obtaining the high-speed rising light output of the present invention using the blue-violet LD will be described. The LD used was threshold current (Ith) 47.79 mA, 5 mW optical output drive current value (Iop5) 52.17 mA, 30 mW optical output drive current value (Iop30) 75.3 mA, 5 mW optical output drive voltage Value (Vop5) 4.21 V, 30 mW light output drive voltage value (Vop30) 4.49 V, 5 mW light output drive resistance value (Rd5) 14.1Ω, 30 mW light output drive resistance value (Rd30) 11.1Ω is there.

In FIG. 11, the first drive current value is a drive current value corresponding to a 4 mW optical output in the IL characteristic curve of the semiconductor LD, and the second drive current value is a drive current waveform corresponding to a drive current corresponding to a 50 mW rating. An optical output waveform is shown.
In FIGS. 11 a), b), and c), only the relative time interval between the first optical output waveform and the second optical output waveform is different, and other driving conditions are exactly the same.

  In FIG. 11a, since the first drive current and the second drive current are sufficiently spaced from each other, the corresponding first light output and second light output are also spaced from each other in time. Yes. It can be seen that there is a very large relaxation oscillation. In FIG. 11b), since the time interval between the first drive current and the second drive current is slightly shorter than in a), the corresponding light outputs are approaching each other, but relaxation oscillation occurs and the present invention. Such a smooth high-speed rise is not realized.

  In FIG. 11c), a drive current in a state where the independent first drive current and the independent second drive current are just joined in time is generated, and LD driving is performed. As can be seen from this figure, in FIG. 11c), the LD light output rise time (Tr) is 0.97 ns, which is not only very fast, but also substantially no relaxation oscillation is observed, and it has been obtained so far. It is one that realizes the earliest rise and realizes an ideal ultrafast pulsed light output waveform.

The procedure for obtaining the ultrafast pulse light output shown here is as follows.
1. The first drive current is set to be applied to the LD as a set value with a drive current of about 3 to 6 mW from the IL curve characteristic. In this embodiment, a drive current value of 51 mA corresponding to 4 mW optical output is applied.
2. The period (Width) in which the first drive current flows is adjusted using a pulse generator, an optical oscilloscope, or the like so that the relaxation oscillation is output once. In this embodiment, the setting is about 6 ns.
3. Next, a current for injecting a desired light output is injected as the second drive current. In the embodiment, 100 mA is applied as a drive current corresponding to an optical output of 50 mW in the IL characteristic curve.
4. Adjust the time so that the rising edge portion of the second driving current approaches the falling edge portion of the first driving current, and from the vicinity of the peak value of the first optical output obtained by the first driving current, Adjust while checking the light output shape with an oscilloscope so that the second light output rises.
In this embodiment, the second drive current falling portion sharply falls to a bias near 0 mA, thereby reducing the influence of current reflection (quenching delay) due to impedance mismatch between the drive circuit and the LD. The light output can be prevented.

  As a result, it has become possible to perform pulse driving in which both the light output rising edge and the light output falling edge are less than 1 nsec, which has been impossible to realize with the nitride semiconductor laser diode.

  In this driving method, relaxation oscillation is induced by the first driving current, and then the laser diode is driven by the second driving current (desired pulse current), so that the superimposed first optical output and second The light output rises at an intermediate level between the relaxation oscillation and the conventionally known rise, whereby a pulse drive having an ultrafast emission rise characteristic can be realized.

  Here, a specific example of the drive circuit according to this embodiment is shown. A conceptual circuit diagram is shown in FIG. 16, and an operation timing chart is shown in FIG. In FIG. 16, the switch 1SW1 (161) becomes OPEN if the signal from the pulse PULSE (1615) is LOW level (for example, 0V), and if the first pulse input (for example, 5V) is input, the constant current source I2 (162). ) Side is switched on, and if the second pulse input is input, the constant current source I3 (163) side is switched on. Also, during the LOW level period between the first and second pulses, OPEN is set as described above.

  When the input of the pulse PULSE is at the LOW level, a voltage generated by flowing a current from an external constant current source I1 (164) to the resistor R1 (165) is converted into an operational amplifier 1OPAMP1 (166), a transistor 1Tr1 (167), and a resistor. 2R2 (168) is input to the voltage-current conversion circuit, whereby a current flows through the transistor 3Tr3 (169). Here, since the transistor 3Tr3 (169) and the transistor 4Tr4 (1610) are current mirror circuits, the same current as the current flowing in the transistor 3Tr3 (169) also flows to the transistor 4Tr4 (1610), and finally The current also flows to the semiconductor laser diode LD (1611) (referred to as Iout1).

  Here, when a HIGH level voltage is input to the pulse PULSE (1615), the switch 1SW1 (161) enters the constant current source I2 (162), and the current corresponding to the current amount of the I2 (162) is changed to the operational amplifier 2OPAMP2 ( 1612), a transistor 2Tr2 (1613) and a resistor 6R6 (1614). Since this current also flows to the transistor 4Tr4 (1610) via the transistor 3Tr3 (169) (this current is referred to as Iout2), it is superimposed on Iout1 described above, and a current of Iout1 + Iout2 flows to the laser.

  Next, after the pulse PULSE (1615) becomes the LOW level and the switch SW1 (161) once becomes OPEN, when the HIGH level voltage is input again, the switch 1SW1 (161) is switched to the constant current source I3 (163). ), And a current corresponding to the amount of current I3 (163) is generated by a voltage-current circuit including an operational amplifier OPAMP2 (1612), a transistor 2Tr2 (1613), and a resistor 6R6 (1614). Since this current also flows to the transistor Tr4 (1610) via the transistor Tr3 (169) (this current is referred to as Iout3), it is superimposed on the Iout1 and a current of Iout1 + Iout3 flows to the semiconductor laser diode. Become. A conceptual timing chart of the above operation is shown in FIG.

Example 4
FIG. 12 shows respective optical output waveforms when the drive current level of the first drive current is increased to a) 49 mA, b) 51 mA, and c) 53 mA in the blue-violet laser diode shown in Example 3. It is. In Example 4, the driving current waveform was stepped. Current drive conditions other than the drive current level of the first drive current are exactly the same, and the bias current is 1 mA.

  In a), the first drive current is set to 49 mA larger than the threshold current (47.79 mA), but this drive current value is lower than b) which is a drive current value corresponding to 4 mW optical output in the IL curve. It is a current value corresponding to 2 mW optical output in the IL curve.

  In b), the first drive current value is 51 mA higher than in a), which corresponds to a current value corresponding to 4 mW optical output of the IL curve. As can be confirmed in the optical output waveform by the oscilloscope, the optical output rise time is 0.97 ns, and the optical output fall time is 0.84 ns, both of which have been known so far. The fastest level of time has been achieved. In the present invention, the pulse drive light output waveform is also a very clean waveform, and no overshoot or undershoot of the light output waveform is observed.

  In c), the value of the first drive current is a drive current value equivalent to 6 mW optical output further increased than in b), and the other drive current conditions are the same. As can be confirmed from the optical output waveform of the oscilloscope, the first oscillation of the first optical output is seen as a small rise. The second optical output is adjusted so that it rises from the first relaxation oscillation falling portion of the first optical output, but the rise time of the optical output is 1.17 ns, and the fall time is also 0. .89 ns, both of which can realize very fast values, and have a very beautiful optical output response waveform in which the effects of relaxation oscillation, overshoot, and undershoot can be substantially ignored.

(Example 5)
In FIG. 13, the first drive current is set as a drive current value corresponding to 4 mW light output in the IL curve of the semiconductor laser diode, and the drive time width of the first drive current is set in the order of a) b) c). An example of the drive current and the light output response waveform when spread is shown as Example 5. The time width of the driving time is a state where a) is about 5 ns, b) is about 6 ns, and the first driving current and the second driving current are joined in an independent state in time a) In addition, the driving time width of the first driving current is increased. Further, c) is about 7 ns, and the driving time width of the first driving current is further increased than in b). In the drive current of c), as can be seen from the schematic diagram, the second half of the first drive current supply time is overlapped and overlapped until after the second drive current supply start time. The total value of the first drive current and the second drive current is supplied for the set time. That is, in order of the time axis, a current of bias current value → first drive current → first and second total drive current value → second drive current value → bias current value is sequentially supplied to the semiconductor LD.

  As shown in the optical output response waveform in this embodiment, a large relaxation oscillation occurs in a), and a large overshoot is observed in the rising state in c). In both cases, the optical output response waveform is a pulsed rectangular wave. is not. On the other hand, in b), the rise time is 0.97 ns, the fall time is 0.84 ns, which is sufficient for high-speed driving, and the light output waveform is also observed for relaxation oscillation, overshoot, and undershoot. A good square wave is not obtained.

  As described above, the adjustment method of the present invention is other than making the relative supply time of the first drive current and the second drive current close (that is, reducing the delay in supplying the second drive current from the first drive current). In addition, the drive supply time of the first drive current is increased as in this embodiment, and as a result, the interval between the drive supply end time of the first drive current and the drive supply start time of the second drive current is increased. It is possible to adjust so that the second light output rises from the first light output so that the second light output is reduced or matched. The reason why the first light output of a) is not observed is considered to be because the supply time of the first drive current is short.

  Here, a structural block conceptual diagram according to another exemplary embodiment of the present invention will be described with reference to FIG. A command (LD drive current value, pulse frequency, etc.) from a personal computer (PC) (211) is sent to a central processing unit (Central) via a serial communication interface (SCI) (212). Processing Unit (hereinafter referred to as “CPU”) (213), and a command from CPU (213) is transmitted as follows.

  The LD drive current value supplied to the semiconductor laser diode (2113) is an indication value (bias current, first drive current, second drive current) from the PC (211) converted to a digital-analog converter (Digital Analog Converter). Thereafter, the signal is transmitted to the LD driving IC (215) through the DAC (214). In addition, the pulse frequency and the pulse width are transmitted from the PC (211) to the variable frequency oscillators (2) and (216) as indicated by the values (frequency and pulse width). The frequency and pulse width of the variable frequency oscillators (1) and (217) are examined in advance using an OOS-1 (186) or the like, and the values are obtained from the PC (211) to the SCI (212) and the CPU. Via (213), it is transmitted to the variable frequency oscillator (1) (217).

  The peak hold circuits (1) and (218) have a smaller capacitor capacity than the peak hold circuits (2) and (219), and are used for detecting the pulse peak value of the optical response due to the first drive current. Since the peak hold circuits (2) and (219) have a large capacitance, they are used to detect the pulse peak value of the optical response due to the second drive current. These two peak hold circuits are triggered by a rising edge detector (2111), and the two peak-held signals are sent to the CPU (213) via an analog-digital converter (ADC) (2110). Is input. The CPU (213) constantly compares the output values of the peak hold circuits (1) (218) and the peak hold circuits (2) (219), and sets the variable frequency oscillators (1) (217) so that the two values are equal. By increasing or decreasing, an optical pulse response having a super-fast rise (1 nsec or less) was realized.

  The ROM (2112) stores a control program for controlling the entire system shown in FIG.

(Comparative Example 1)
As a comparative example 1 in FIG. 14, in the case of driving a step-type pulse current, that is, in a driving current in which the first driving current and the second driving current are just joined in time, the first driving current value An example when the level is changed is shown. The first drive current value of a) is about 47 mA below the threshold value. b) shows a case where the first drive current value is set to about 51 mA, and c) shows about 53 mA. All other drive conditions are the same. As can be seen from the optical output response waveforms corresponding to a), b) and c), respectively, the first drive current is set to a low value below the threshold value in a). The second optical output at the second driving current substantially becomes a response rise with relaxation oscillation as the first pulse. Subsequently, in b), the first drive current setting of about 51 mA corresponding to the 4 mW optical output in the IL curve is set, but the first optical output is observed independently of the second optical output. Since the second light output is not adjusted to rise from the first light output, the light output rise is about 1.45 ns, which is slightly delayed.

  Further, in c), since the first drive current is further increased, the corresponding first light output is also clearly observed. However, as in b), the light output rise in this case is 1.75 ns, which is inferior in terms of speeding up.

  As shown in the above-mentioned Examples and Comparative Examples, in the present invention, as a most preferable embodiment, the first drive current value is set to 3 to 6 mW optical output equivalent value of the IL characteristic curve of the semiconductor laser diode or rated light. The drive current value corresponding to the optical output of about 10% to 20% of the output is set, and the relative supply timing time of the first drive current and the second drive current is appropriately adjusted, so that high-speed rise and overshoot A pulsed light output waveform without undershoot and relaxation oscillation can be realized, and the adjusted optimum timing time and the like differ for each semiconductor LD type. However, if the LD frequency response characteristics are improved The first drive current supply time tends to be shorter.

  Further, in the pulse drive circuit shown in FIG. 15, first, focusing on the left side of the current mirror circuit, when the second drive current is supplied in the fourth embodiment, the Iout1 bias current and the Iout3 second current are superimposed. Since the first current Iout2 is stopped, in the fourth embodiment, the three transistors of the transistor 1 (Tr1) 157, the transistor 3 (Tr3) 1519, and the transistor 4 (Tr4) 159 are turned on to be in an operating state. 2 (Tr2) 1514 is in an OFF state.

  On the other hand, in the first comparative example, when the second drive current is supplied, the Iout1 bias current, the Iout2 first drive current, and the Iout3 second drive current are superimposed, so that the transistor 1 (Tr1) 157 and the transistor 2 ( The four transistors Tr2) 1514, transistor 3 (Tr3) 1519, and transistor 4 (Tr4) 159 are turned on and are in operation. As a result, comparing the capacitor components such as parasitic capacitance and stray capacitance in the current path during the driving of the fourth embodiment and the first comparative example, the first comparative example has a larger number of transistors, so that the capacitor capacity becomes larger and responds to pulses. It is considered that the response speed of the drive current is faster in the fourth embodiment because the parasitic capacitance is smaller.

  Correspondingly, it is considered that the response drive speed corresponding to the pulse of the transistor 5 (Tr5) 1510 on the right side of the current mirror circuit is also faster in the fourth embodiment than in the first comparative example. In order to drive the laser diode at an ultra-high speed, the fourth embodiment using a drive circuit with a small number of capacitor components, typically a small number of transistors that form a parasitic capacitance, is considered to be a more preferable drive mode. Yes.

  The output stage transistor (transistor directly driving the laser diode (corresponding to the transistor (Tr5) 1510 in the circuit example of FIG. 15)) is more preferably a circuit driven by an NPN transistor or an N-channel transistor. . That is, since the NPN transistor and the N channel transistor have electrons as carriers, the mobility is higher than that of the PNP transistor or P channel transistor in which the carriers are holes, and the cutoff frequency (cutoff frequency) is also large. Since the falling response speed can be further increased and the pulse emission response rise and fall can be accelerated, the laser diode can be driven at a higher speed, and a more preferable result can be obtained.

  Furthermore, the driving method and driving circuit of the present invention can also be applied to a semiconductor laser diode (light emission color is not limited) that has a very good frequency response characteristic and is used in communication systems, etc. More favorable results can be obtained in terms of the light emission rise characteristics of the semiconductor laser diode.

Apparatus for supplying driving current to a conventional semiconductor laser (A) Rectangular pulse current which is a conventional semiconductor laser driving current (b) Relaxation oscillation of conventional semiconductor laser light output IL characteristic curve of semiconductor laser and threshold current (Ith) Schematic diagram related to one embodiment of the drive current waveform Schematic conceptual diagram showing rounding of semiconductor laser light output Laser drive current waveform schematic diagram according to an embodiment of the present invention Circuit configuration diagram according to the second embodiment Equivalent circuit of semiconductor laser Typical example showing relationship between drive current and optical output waveform according to the present invention Schematic diagram of adjusting method of first driving current and second driving current of the present invention Conceptual diagram of drive current waveform and optical output response waveform related to Example 3 Schematic diagram of drive current waveform and optical output response waveform related to Example 4 Conceptual diagram of drive current waveform and optical output response waveform related to Example 5 Optical output response waveform for Comparative Example 1 Circuit explanatory diagram according to the second embodiment Circuit explanatory diagram related to Example 3 Operation timing chart conceptual diagram related to the circuit schematic of FIG. Circuit connection schematic structure diagram of embodiment of the present invention related to Example 1 Conceptual diagram of operation timing chart of the present invention related to Example 1 shown in FIG. Another operation timing chart conceptual diagram of the present invention related to Example 1 Typical example The circuit block conceptual diagram in connection with one Embodiment of this invention

Explanation of symbols

151... Switch 1
152 ... Pulse 1
153: Switch 2
154 ... Constant current source I1
155: Resistor R1
156: operational amplifier 1
157 ... Transistor 1
158... Resistance 2
159 ... Transistor 4
1510... Transistor 5
1511: Semiconductor laser diode 1512 ... Current I2
1513... Operational amplifier 2
1514 ... Transistor 2
1515... Resistance 4
1516: Pulse 2
1517 ... Current I3
1518: operational amplifier 3
1519 ... Transistor 3
1520: Resistance 6
161: Switch 1
162... Constant current source I2
163: Constant current source I3
164 ... Constant current source I1
165: Resistor R1
166... Operational amplifier 1 OPAMP1
167 ... Transistor 1Tr1
168: Resistance R2
169 ... Transistor 3Tr3
1610 ... Transistor 4Tr4
1611: Semiconductor laser diode 1612: Operational amplifier 2OPAMP2
1613 ... Transistor 2Tr2
1614... Resistance R6
1615 ... Pulse PULSE
180 ... pulse generator 181 ... pulse Pulse1
182 ... Pulse Pulse 2
183 ... Constant current source 1 (I1)
184 ... Constant current source 2 (I2)
185 ... Constant current source 3 (I3)
186 ... Pulse emission waveform measuring instrument 187 ... Semiconductor laser diode current drive IC
188 ... IC current output Iout
1811 ... Semiconductor laser diode 211 ... Personal computer (PC)
212 ... Serial Communication Interface (SCI)
213... Central processing unit (CPU)
214 ... Digital-analog converter (DAC)
215 ... Semiconductor laser diode current drive IC
216 ... Variable frequency oscillator (2)
217 ... Variable frequency oscillator (1)
218 ... Peak hold circuit (1)
219 ... Peak hold circuit (2)
2110 ··· Analog to Digital Converter (ADC)
2111 ... Rising edge detector 2112 ... Storage device (ROM, etc.)

Claims (8)

A method of driving a semiconductor laser diode, wherein the semiconductor laser diode emits light through a drive circuit,
The method of driving the semiconductor laser diode is as follows:
A first step of applying a first drive current from the drive circuit to the semiconductor laser diode;
Applying a second drive current from the drive circuit to the semiconductor laser diode subsequent to the first drive current; and
The first light output corresponding to the first drive current and the second light output corresponding to the second drive current are superimposed and output as a one-pulse light output,
A driving method of a semiconductor laser diode, wherein the second light output rises from a maximum value in relaxation oscillation of the first light output so as to be larger than a peak value of the relaxation oscillation. 2. The method of driving a semiconductor laser diode according to claim 1, wherein a current value of the first drive current is smaller than a current value of the second drive current. 3. The method of driving a semiconductor laser diode according to claim 1 , wherein a bias current is supplied superimposed on the first driving current and the second driving current. 4. 4. The method of driving a semiconductor laser diode according to claim 1 , wherein the supply time of the first drive current and the supply time of the second drive current are supply times independent of each other. A semiconductor laser diode light emitting device comprising: a semiconductor laser diode; and a drive circuit for driving the semiconductor laser diode,
The light emitting device of the semiconductor laser diode is
First current application means for applying a first drive current from the drive circuit to the semiconductor laser diode;
Second current applying means for applying a second drive current from the drive circuit to the semiconductor laser diode following the first drive current;
Storage means for storing desired data output as a one-pulse optical output by superimposing a first optical output corresponding to the first driving current and a second optical output corresponding to the second driving current And having
A light emitting device for a semiconductor laser diode, wherein the second light output rises from a maximum value in the relaxation oscillation of the first light output so as to be larger than a peak value of the relaxation oscillation. 6. The semiconductor laser diode light emitting device according to claim 5 , wherein a current value of the first drive current is smaller than a current value of the second drive current. The light emitting device for a semiconductor laser diode according to claim 5, further comprising a bias current supply circuit that supplies a bias current superimposed on the first drive current and the second drive current. 8. The light emitting device for a semiconductor laser diode according to claim 5 , wherein the supply time of the first drive current and the supply time of the second drive current are supply times independent of each other.

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