Q-switching method of laser

Abstract

The invention relates to a Q-switching method of a laser, and the method comprises the steps: increasing the driving voltage of an electro-optical switch, carrying out the two or more times of quick Q-switching in one step-up process, and carrying out the special limitation of the on-off state of the electro-optical switch according to the transition characteristics of energy level particles, thereby achieving the double-pulse output or multi-pulse output of laser. As the boosting time is in a nanosecond level, nanosecond level pulse interval output is realized. The pulse interval laser is intermediate frequency laser, and compared with laser in a traditional single-pulse and multi-pulse mode, the laser in the mode can improve the application efficiency, such as laser freckle removing or laser skin tendering, so that many application requirements of the industry are met.

Description

Technical Field

[0001] The invention relates to the field of laser technology, and in particular to a Q-switching method for a laser. Background Art

[0002] Electro-optical Q-switching technology is a mainstream technical solution for pulsed lasers and can be widely used in different industries. Nd:YAG electro-optical Q-switched lasers based on xenon lamp pumping are widely used in the field of medical beauty, such as freckle removal and skin rejuvenation. Existing lasers can already output single pulse lasers, dual pulse lasers, and multi-pulse lasers.

[0003] like Figure 1 As shown, the conventional xenon lamp-pumped electro-optical Q-switched laser can output a single pulse laser. When outputting a single pulse, the xenon lamp flashes after receiving the xenon lamp pumping voltage 21, and the xenon lamp pumping voltage 21 is in the order of hundreds of microseconds. When the electro-optical switch driving voltage does not drive the electro-optical switch, the electro-optical switch is in the "off" state. When the electro-optical switch driving voltage 22 drives the electro-optical switch to open, the electro-optical switch driving voltage 22 is a 1 / 4 wave voltage, and a single pulse 23 is output. The above electro-optical Q-switching method can obtain

[0004] like Figure 2 As shown, the conventional xenon lamp-pumped electro-optical Q-switched laser can output a double-pulse laser. When outputting double pulses, the xenon lamp flashes after receiving the xenon lamp pumping voltage 31, and the xenon lamp pumping voltage 31 is in the order of hundreds of microseconds. When the electro-optical switch driving voltage does not drive the electro-optical switch, the electro-optical switch is in the "off" state. When the electro-optical switch driving voltage 331 drives the electro-optical switch to open, the electro-optical switch driving voltage 321 is a 1 / 4 wave voltage, and the first sub-pulse 331 is output at this time, and then the electro-optical switch driving voltage 321 drops to 0, and the electro-optical switch is "off"; the electro-optical switch driving voltage 332 drives the electro-optical switch to open, and the electro-optical switch driving voltage 322 is a 1 / 4 wave voltage, and the second sub-pulse 332 is output. The above electro-optical Q-switching method can obtain a double-pulse laser, but the double-pulse laser pulse interval is in the microsecond order.

[0005] Although the above-mentioned existing Q-switched lasers can already obtain high-efficiency single-pulse lasers and double-pulse lasers, in most application fields, laser energy and repetition rate determine their application efficiency, so the industry pursues outputs with greater energy and greater repetition rate. However, most lasers are currently limited by their own technical principles, and it is difficult to increase the repetition rate. For example, the Nd:YAG electro-optical Q-switched laser based on xenon lamp pumping, the xenon lamp repetition frequency can meet the high-energy nanosecond laser output while failing to achieve high repetition frequency output. The general repetition frequency can only reach a maximum of ten hertz. The laser with this pulse interval is relatively "low-frequency laser", which is difficult to meet the application needs of many industries. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a Q-switching method for a laser that can generate multiple pulses with nanosecond intervals to meet the needs of more industries in view of the current status of the prior art.

[0007] The technical solution adopted by the present invention to solve the above technical problems is:

[0008] A laser Q-switching method, which increases the driving voltage of an electro-optical switch and performs multiple Q-switching in one voltage-boosting process to obtain at least two laser sub-pulses;

[0009] The number of laser pulses obtained is n, and the electro-optical switch driving voltage is U, U ≥ (2n-1) / 4 wave voltage, wherein n is a positive integer ≥ 1;

[0010] The electro-optical switch driving voltage U≥3 / 4; in the signal rising edge stage of the electro-optical switch driving voltage, when U=m' / 4 wave voltage, the electro-optical switch is in the open state, and when U=m" / 4 wave voltage, the electro-optical switch is in the closed state; wherein, m', m"∈[1,2n-1], and m"-m'=1.

[0011] Preferably, m' is an odd number and m" is an even number. Using such parameters is conducive to more compactly realizing the output of laser multi-pulses.

[0012] Preferably, the signal rising edge time of the electro-optical switch driving voltage is in the nanosecond level, and the signal falling edge time of the electro-optical switch driving voltage is in the microsecond level.

[0013] Preferably, in the Q-switching process, the number of upper energy level particles of n laser pulses is distributed on demand by controlling the rising edge time of the signal of the electro-optical switch driving voltage, thereby controlling the size ratio of the n sub-pulses. Specifically, in the actual control process, the rising edge time of the Q-switch driving signal given by the Q-switching module can be controlled by changing the opening time of the MOS tube.

[0014] As a preferred solution: n=2, U=3 / 4 or 3 / 4<U<5 / 4; this parameter is suitable for outputting laser double pulses;

[0015] The xenon lamp flashes after receiving the xenon lamp pumping voltage, and the laser gain medium in the laser receives the xenon lamp pumping light, resulting in energy level transition, and the lower energy level particles transition to the upper energy level. When the electro-optic switch driving voltage does not drive the electro-optic switch, the electro-optic switch is in the closed state, the laser does not emit light, and the upper energy level particles of the gain medium gradually gather;

[0016] When the energy level particles on the gain medium gather to a certain amount, the electro-optic switch driving voltage drives the electro-optic switch. During the rising edge of the voltage signal of the electro-optic switch driving voltage, it sequentially experiences 1 / 4 wave voltage, 1 / 2 wave voltage, and 3 / 4 wave voltage. When the electro-optic switch driving voltage increases to 1 / 4 wave voltage, the electro-optic switch is in an "on" state. When the electro-optic switch driving voltage increases to 1 / 2 wave voltage, the electro-optic switch is in a "off" state. When the electro-optic switch driving voltage increases to 3 / 4 wave voltage, the electro-optic switch is in an "on" state again.

[0017] In the above process, when the electro-optical switch driving voltage increases to 1 / 4 wave voltage, the electro-optical switch is in the "on" state, and the upper energy level particles of the laser gathered in the gain medium transition downward to form the first sub-pulse output of the laser double pulse; when the electro-optical switch is "turned on" for the first time, the upper energy level particles of the gain medium have not had time to be completely converted into laser output, the electro-optical switch driving voltage rises to 1 / 2 wave voltage, and the electro-optical switch is "turned off". When the voltage increases to 3 / 4 wave voltage, the electro-optical switch is "turned on" again, and the remaining upper energy level particles of the gain medium transition downward to form the second sub-pulse output of the laser double pulse.

[0018] As another preferred solution: n=3, U=5 / 4 or 5 / 4<U<7 / 4; this parameter is suitable for outputting three laser pulses;

[0019] The xenon lamp flashes after receiving the xenon lamp pumping voltage, and the laser gain medium in the laser receives the xenon lamp pumping light, resulting in energy level transition, and the lower energy level particles transition to the upper energy level. When the electro-optic switch driving voltage does not drive the electro-optic switch, the electro-optic switch is in the closed state, the laser does not emit light, and the upper energy level particles of the gain medium gradually gather;

[0020] When the energy level particles on the gain medium gather to a certain amount, the electro-optic switch driving voltage drives the electro-optic switch. During the rising edge of the voltage signal of the electro-optic switch driving voltage, it sequentially experiences 1 / 4 wave voltage, 1 / 2 wave voltage, 3 / 4 wave voltage, 1 wave voltage, and 5 / 4 wave voltage. When the electro-optic switch driving voltage increases to 1 / 4 wave voltage, the electro-optic switch is in an "on" state. When the electro-optic switch driving voltage increases to 1 / 2 wave voltage, the electro-optic switch is in a "off" state. When the electro-optic switch driving voltage increases to 3 / 4 wave voltage, the electro-optic switch is in an "on" state. When the electro-optic switch driving voltage increases to 1 wave voltage, the electro-optic switch is in a "off" state. When the electro-optic switch driving voltage increases to 5 / 4 wave voltage, the electro-optic switch is in an "on" state.

[0021] In the above process, when the electro-optical switch driving voltage increases to 1 / 4 wave voltage, the electro-optical switch is in the "on" state, and the laser upper energy level particles gathered in the gain medium transition downward to form the first sub-pulse output of the laser double pulse; when the electro-optical switch is "on" for the first time, the upper energy level particles of the gain medium have not had time to be completely converted into laser output, the electro-optical switch driving voltage increases to 1 / 2 wave voltage, and the electro-optical switch is "closed". When the voltage increases to 3 / 4 wave voltage, the electro-optical switch is "on" again, and the remaining upper energy level particles of the gain medium transition downward to form the second sub-pulse output of the laser double pulse; when the electro-optical switch is "on" for the second time, the upper energy level particles of the gain medium have not had time to be completely converted into laser output, the electro-optical switch driving voltage increases to 1 wave voltage, and the electro-optical switch is "closed". When the voltage increases to 5 / 4 wave voltage, the electro-optical switch is "on" again, and the remaining upper energy level particles of the gain medium transition downward to form the third sub-pulse output of the laser double pulse.

[0022] Compared with the prior art, the advantages of the present invention are: the present invention increases the driving voltage of the electro-optical switch, performs two or more rapid Q-switching in a boosting process, and places special restrictions on the on and off states of the electro-optical switch according to the transition characteristics of the energy level particles, thereby achieving double-pulse output or multi-pulse output of the laser. Since the boosting time is in the nanosecond level, nanosecond pulse interval output is achieved. The pulse interval laser of the present invention is a "medium frequency laser". Compared with the traditional single-pulse and multi-pulse mode lasers, this mode of laser can improve the application efficiency, such as laser freckle removal or laser skin rejuvenation, to meet many application needs of the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of the Q-switching principle of the background technology of the present invention;

[0024] Figure 2 It is another schematic diagram of Q-switching principle of the background technology of the present invention;

[0025] Figure 3 This is a schematic diagram of the Q-switching principle of Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings.

[0027] Embodiment 1:

[0028] The Q-switching method of the laser in this embodiment can obtain nanosecond laser double pulses or multiple pulses.

[0029] The Q-switching method of the laser in this embodiment increases the driving voltage of the electro-optical switch and performs multiple Q-switching in one voltage-boosting process to obtain at least two laser sub-pulses;

[0030] The number of laser pulses obtained is n, and the driving voltage of the electro-optical switch is U, U ≥ (2n-1) / 4 wave voltage, where n is a positive integer ≥ 1;

[0031] The electro-optical switch driving voltage U≥3 / 4; in the rising edge stage of the electro-optical switch driving voltage signal, when U=m' / 4 wave voltage, the electro-optical switch is in the open state, and when U=m" / 4 wave voltage, the electro-optical switch is in the closed state; wherein, m', m"∈[1,2n-1], and m"-m'=1.

[0032] Specifically, m' is an odd number and m" is an even number. Using such parameters is conducive to realizing the output of laser multi-pulses more compactly.

[0033] The signal rising edge time of the electro-optical switch driving voltage is in the nanosecond level, and the signal falling edge time of the electro-optical switch driving voltage is in the microsecond level.

[0034] In the Q-switching process, the number of upper energy level particles of n laser pulses is distributed on demand by controlling the signal rising edge time of the electro-optic switch driving voltage, thereby controlling the size ratio of the n sub-pulses.

[0035] This embodiment specifically provides a Q-switching method for obtaining laser double pulses:

[0036] n = 2, U = 3 / 4 or slightly greater than 3 / 4;

[0037] like Figure 3 As shown, the xenon lamp flashes after receiving the xenon lamp pump voltage 11, and the laser gain medium in the laser receives the xenon lamp pump light, resulting in energy level transition, and the lower energy level particles transition to the upper energy level. When the electro-optic switch driving voltage does not drive the electro-optic switch, the electro-optic switch is in the closed state, the laser does not emit light, and the upper energy level particles of the gain medium gradually gather;

[0038] When the energy level particles on the gain medium gather to a certain amount, the electro-optic switch driving voltage 12 drives the electro-optic switch. During the rising edge of the voltage signal of the electro-optic switch driving voltage, it sequentially experiences 1 / 4 wave voltage, 1 / 2 wave voltage, and 3 / 4 wave voltage. When the electro-optic switch driving voltage increases to 1 / 4 wave voltage, the electro-optic switch is in an "on" state. When the electro-optic switch driving voltage increases to 1 / 2 wave voltage, the electro-optic switch is in a "off" state. When the electro-optic switch driving voltage increases to 3 / 4 wave voltage, the electro-optic switch is in an "on" state again.

[0039] In the above process, when the electro-optical switch driving voltage increases to 1 / 4 wave voltage, the electro-optical switch is in the "on" state, and the upper energy level particles of the laser gathered in the gain medium transition downward to form the first sub-pulse 131 of the laser double pulse output; when the electro-optical switch is "on" for the first time, the upper energy level particles of the gain medium have not had time to be converted into laser output, the electro-optical switch driving voltage 12 rises to 1 / 2 wave voltage, and the electro-optical switch is "closed". When the voltage increases to 3 / 4 wave voltage, the electro-optical switch is "on" again, and the remaining upper energy level particles of the gain medium transition downward to form the second sub-pulse 132 of the laser double pulse output.

[0040] Embodiment 2:

[0041] The difference between this embodiment and embodiment 1 is that this embodiment provides a Q-switching method for obtaining three laser pulses:

[0042] n=3,U=5 / 4 or slightly larger than 5 / 4;

[0043] The xenon lamp flashes after receiving the xenon lamp pumping voltage, and the laser gain medium in the laser receives the xenon lamp pumping light, resulting in energy level transition, and the lower energy level particles transition to the upper energy level. When the electro-optic switch driving voltage does not drive the electro-optic switch, the electro-optic switch is in the closed state, the laser does not emit light, and the upper energy level particles of the gain medium gradually gather;

[0044] When the energy level particles on the gain medium gather to a certain amount, the electro-optic switch driving voltage drives the electro-optic switch. During the rising edge of the voltage signal of the electro-optic switch driving voltage, it sequentially experiences 1 / 4 wave voltage, 1 / 2 wave voltage, 3 / 4 wave voltage, 1 wave voltage, and 5 / 4 wave voltage. When the electro-optic switch driving voltage increases to 1 / 4 wave voltage, the electro-optic switch is in an "on" state. When the electro-optic switch driving voltage increases to 1 / 2 wave voltage, the electro-optic switch is in a "off" state. When the electro-optic switch driving voltage increases to 3 / 4 wave voltage, the electro-optic switch is in an "on" state. When the electro-optic switch driving voltage increases to 1 wave voltage, the electro-optic switch is in a "off" state. When the electro-optic switch driving voltage increases to 5 / 4 wave voltage, the electro-optic switch is in an "on" state.

[0045] In the above process, when the electro-optical switch driving voltage increases to 1 / 4 wave voltage, the electro-optical switch is in the "on" state, and the laser upper energy level particles gathered in the gain medium transition downward to form the first sub-pulse output of the laser double pulse; when the electro-optical switch is "on" for the first time, the upper energy level particles of the gain medium have not had time to be completely converted into laser output, the electro-optical switch driving voltage increases to 1 / 2 wave voltage, and the electro-optical switch is "closed". When the voltage increases to 3 / 4 wave voltage, the electro-optical switch is "on" again, and the remaining upper energy level particles of the gain medium transition downward to form the second sub-pulse output of the laser double pulse; when the electro-optical switch is "on" for the second time, the upper energy level particles of the gain medium have not had time to be completely converted into laser output, the electro-optical switch driving voltage increases to 1 wave voltage, and the electro-optical switch is "closed". When the voltage increases to 5 / 4 wave voltage, the electro-optical switch is "on" again, and the remaining upper energy level particles of the gain medium transition downward to form the third sub-pulse output of the laser double pulse.

[0046] It should be noted that the method of the present invention is not only applicable to electro-optical Q-switching, but also applicable to other Q-switched lasers.

[0047] The embodiment of the present invention increases the driving voltage of the electro-optical switch, performs two or more rapid Q-switching in a boosting process, and places special restrictions on the on and off states of the electro-optical switch according to the transition characteristics of the energy level particles, thereby achieving dual-pulse output or multi-pulse output of the laser. Since the boosting time is in the nanosecond level, nanosecond pulse interval output is achieved. The pulse interval laser of the embodiment of the present invention is a "medium frequency laser". Compared with the traditional single-pulse and multi-pulse mode lasers, this mode of laser can improve the application efficiency, such as laser freckle removal or laser skin rejuvenation, to meet many application needs of the industry.

Claims

1. A Q-switching method for a laser, characterized in that: At least two laser sub-pulses are obtained by increasing the driving voltage of the electro-optical switch and performing multiple Q-switching in one voltage-boosting process; The number of laser pulses obtained is n, and the electro-optical switch driving voltage is U, U ≥ (2n-1) / 4 wave voltage, wherein n is a positive integer ≥ 1; The electro-optical switch driving voltage U≥3 / 4; in the signal rising edge stage of the electro-optical switch driving voltage, when U=m' / 4 wave voltage, the electro-optical switch is in the open state, and when U=m" / 4 wave voltage, the electro-optical switch is in the closed state; wherein, m', m"∈[1,2n-1], and m"-m'=1.

2. The Q-switching method of a laser according to claim 1, characterized in that: m' is an odd number, and m" is an even number.

3. The Q-switching method of a laser according to claim 1, characterized in that: The signal rising edge time of the electro-optical switch driving voltage is in the nanosecond level, and the signal falling edge time of the electro-optical switch driving voltage is in the microsecond level.

4. The Q-switching method of a laser according to claim 1, characterized in that: In the Q-switching process, the number of upper energy level particles of n laser pulses is distributed as needed by controlling the signal rising edge time of the electro-optic switch driving voltage, thereby controlling the size ratio of the n sub-pulses.

5. The Q-switching method of a laser according to any one of claims 1 to 4, characterized in that: n=2, U=3 / 4 or 3 / 4<U<5 / 4; The xenon lamp flashes after receiving the xenon lamp pumping voltage, and the laser gain medium in the laser receives the xenon lamp pumping light, resulting in energy level transition, and the lower energy level particles transition to the upper energy level. When the electro-optic switch driving voltage does not drive the electro-optic switch, the electro-optic switch is in the closed state, the laser does not emit light, and the upper energy level particles of the gain medium gradually gather; When the energy level particles on the gain medium gather to a certain amount, the electro-optic switch driving voltage drives the electro-optic switch. During the rising edge of the voltage signal of the electro-optic switch driving voltage, it experiences 1 / 4 wave voltage, 1 / 2 wave voltage, and 3 / 4 wave voltage in sequence. When the electro-optic switch driving voltage increases to 1 / 4 wave voltage, the electro-optic switch is in the "on" state. When the electro-optic switch driving voltage increases to 1 / 2 wave voltage, the electro-optic switch is in the "off" state. When the electro-optic switch driving voltage increases to 3 / 4 wave voltage, the electro-optic switch is in the "on" state again. In the above process, when the electro-optic switch driving voltage increases to 1 / 4 wave voltage, the electro-optic switch is in the "on" state, and the upper energy level particles of the laser gathered in the gain medium transition downward to form the first sub-pulse output of the laser double pulse; when the electro-optic switch is "on" for the first time, the upper energy level particles of the gain medium have not had time to be converted into laser output, the electro-optic switch driving voltage rises to 1 / 2 wave voltage, and the electro-optic switch is "closed". When the voltage increases to 3 / 4 wave voltage, the electro-optic switch is "opened" again, and the remaining upper energy level particles of the gain medium transition downward to form the second sub-pulse output of the laser double pulse.

6. The Q-switching method of a laser according to any one of claims 1 to 4, characterized in that: n=3, U=5 / 4 or 5 / 4<U<7 / 4; The xenon lamp flashes after receiving the xenon lamp pumping voltage, and the laser gain medium in the laser receives the xenon lamp pumping light, resulting in energy level transition, and the lower energy level particles transition to the upper energy level. When the electro-optic switch driving voltage does not drive the electro-optic switch, the electro-optic switch is in the closed state, the laser does not emit light, and the upper energy level particles of the gain medium gradually gather; When the energy level particles on the gain medium gather to a certain amount, the electro-optic switch driving voltage drives the electro-optic switch. During the rising edge of the voltage signal of the electro-optic switch driving voltage, it sequentially experiences 1 / 4 wave voltage, 1 / 2 wave voltage, 3 / 4 wave voltage, 1 wave voltage, and 5 / 4 wave voltage. When the electro-optic switch driving voltage increases to 1 / 4 wave voltage, the electro-optic switch is in the "on" state. When the electro-optic switch driving voltage increases to 1 / 2 wave voltage, the electro-optic switch is in the "off" state. When the electro-optic switch driving voltage increases to 3 / 4 wave voltage, the electro-optic switch is in the "on" state. When the electro-optic switch driving voltage rises to the 1-wave voltage, the electro-optic switch is in the "off" state; When the electro-optic switch driving voltage increases to a 5 / 4 wave voltage, the electro-optic switch is in the "on" state; In the above process, when the electro-optical switch driving voltage increases to 1 / 4 wave voltage, the electro-optical switch is in the "on" state, and the laser upper energy level particles gathered in the gain medium transition downward to form the first sub-pulse output of the laser double pulse; when the electro-optical switch is "on" for the first time, the upper energy level particles of the gain medium have not had time to be fully converted into laser output, the electro-optical switch driving voltage increases to 1 / 2 wave voltage, and the electro-optical switch is "closed". When the voltage increases to 3 / 4 wave voltage, the electro-optical switch is "on" again, and the remaining upper energy level particles of the gain medium transition downward to form the second sub-pulse output of the laser double pulse; when the electro-optical switch is "on" for the second time, the upper energy level particles of the gain medium have not had time to be fully converted into laser output, the electro-optical switch driving voltage increases to 1 wave voltage, and the electro-optical switch is "closed". When the voltage increases to 5 / 4 wave voltage, the electro-optical switch is "on" again, and the remaining upper energy level particles of the gain medium transition downward to form the third sub-pulse output of the laser double pulse.

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