TW465153B - Self-hybrid mode-locking method for generating laser - Google Patents

Abstract

A self-hybrid mode-locking method for generating laser, applicable to a semiconductor laser or a semiconductor laser amplifier, comprises the following steps: (1) applying a DC bias current to the semiconductor laser or the semiconductor laser amplifier where the DC bias current is higher than the threshold current of the semiconductor laser or the semiconductor laser amplifier; and (2) applying a RF modulation signal to the semiconductor laser or the semiconductor laser amplifier where the RF modulation current is higher than the difference between the DC current and the transparent current of the semiconductor laser. When RF modulation signal is at the gain maximum value, the semiconductor laser is compressed to generate a pulse laser, and then, when RF modulation signal is at the gain minimum value, the semiconductor laser becomes a saturable absorber and is compressed to generate a pulse laser.

Description

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4 65 1 Special ί = related to-a method of self-contained mode-locked laser generation, general semiconductor laser is used for physical force, no saturable absorption is required, a proper DC bias current and radio frequency (radi0 frequency (RF for short) modulating signals, semiconductor lasers become mode-locked pulse lasers. Disaster-producing milk has been widely used in recent years. The research on short-pulse lasers has been widely used in optical communications, chemical reaction measurement, physical measurement, and distance measurement. It has long attracted the interest of many industries and researchers. The button pulse method is generally classified as gain-switching or Q-switching and mode locking

Uodtlocking). Compared to gain switching, the mode-locked method can produce shorter pulse lasers. The mode locking can be further divided into the following ways: active mode-locking, passive mode (passive heart-10cJiing) and hybrid mode (hybrid in 〇de _ i 〇cking) 13 As the first The pulse timing diagram of a conventional active mode-locking shown in Fig. 1 e The modulation frequency of the RF is the same as the pulse repetition rate. When the pulse laser starts from the semiconductor laser amplifier at the modulation frequency peak and returns to the semiconductor laser amplifier via mirror reflection, the pulse laser and the modulation frequency peak overlap again, so that the peak value of the pulse laser is amplified by the gain. Stronger than the edges of a pulsed laser. Therefore, after complex resonance, a short pulse laser can be generated. Active mode-locking can produce pulse lasers with minimal timing jitter, while passive mode-locking can produce shorter pulse lasers. Hybrid mode-locking

Page 4 4 65 1 5 ^ V. Description of the Invention (2) Month b takes into account both the advantages of passive mode-locked laser and active mode-locked laser, which can produce pulse laser with very short time and very small time jitter. However, there are disadvantages to hybrid mold clamping. It requires quite complex and specially designed saturable absorbers to successfully achieve hybrid mode-locking. The typical components used for hybrid mold clamping are multi-segment, multi-electrode components, which are more difficult and complicated compared to other mold clamping methods. In view of this, 'the present invention proposes a new mode-locking technology and solves the above-mentioned door pass. The present invention is a self-mixing mode-locking (seif-hybrid mode-.locking) laser generation method', which is suitable for a semiconductor laser. Or two semiconductor laser amplifiers, including the following steps. (1) Apply a DC bias to a far semiconductor laser or semiconductor laser amplifier, where the DC bias value is greater than the threshold, k, of the semiconductor laser or the semiconductor laser amplifier. (2) An RF modulation signal is applied to the semiconductor laser or semiconductor, wherein the kf modulation current value is greater than the difference between the DC current value and its transparent current value. Beware that the modulation signal is a gain laser compression pulse to generate a pulse laser. The modulation signal produces: 冲 雷 laser: a semiconductor laser is converted into a saturable absorber and compressed ，: ΐ 玩 ίί invention Just use a single electrode semiconductor laser. So: it can get mixed mode-locked pulse laser with absorber, so it is called self-mixed mode-locked. The drawings are simply explained. Understand that the features and advantages of ΐίίΠί can be more obvious and easier. The following is a detailed description of the preferred embodiment and the accompanying drawings. [465153 V. Description of the invention (3) is as follows:

A periodic non-sinusoidal wave is used in this embodiment. Fig. 1 is a conventional master. Fig. 2 shows a structure diagram of a laser cavity of the present invention which is more interesting. Figure 3 illustrates the preferred embodiment of the present invention. Figure 4 illustrates the self-mixing of the present invention. Figure 5 illustrates the preferred embodiment of the present invention. Fig. 6 is a preferred view of the present invention. Figure 7 shows a timing diagram of applying a pulsed laser. Symbol description Timing diagram of mode-locked pulse laser. The self-mixing of the embodiment generates the mode-locking pulse. The technical principle of the embodiment. Timing diagram of pulse-locked laser. Half-width of the autocorrelation track pulse of the embodiment

10 ~ laser cavity; 20 ~ semiconductor laser amplifier; 30 ~ collimating lens; 40 ~ grating; 50 ~ output coupler; 60a ~ lens; 60b ~ lens; 1 modulation electric grip, itr ~ Transparent current; ~ DC bias current; ^ wide gain value; G "in ~ gain valley value; 1R ~ right arm length; 1L ~ left arm length ^ Description of preferred embodiments

As shown in FIG. 2, a structure diagram of a laser cavity 10 for self-mixing mold clamping according to a preferred embodiment of the present invention. In the present embodiment, the laser cavity 10 includes a superiuminescent diode amplifier 20, a complex collimator lens 30, a grating 40, and a round-out coupler 50. As shown in the preferred embodiment of the present invention, the gain element is 54 mm

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Modification J · »· ，， ·· &quot; V. Description of the Invention (4) The super-brightness semiconductor laser amplifier 20 of the beveled ridge waveguide 22 of the invention. The angle between the waveguide 22 and the mirror normal is 7 degrees. The waveguide 22 in this embodiment does not require additional anti-reflection coating (AR coating), because the inclined waveguide angle can reverse the mirror surface and reduce the rate to less than 1 / 10,000. After the laser light starts from the ultra-brightness semiconductor laser amplifier 20, it is collimated to form a parallel light through a numerical aperture (cojUmator l.ens) 30 with a numerical aperture CU ^ "^, and then diffracted through a gold-plated every 1200 diffraction A grating 4Q reflects light of a specific wavelength and returns to the super-brightness semiconductor laser amplifier 20. The grating 40 is used to reflect light of a specific wavelength back to the super-brightness semiconductor laser amplifier 0 ′ and has a frequency Wide-limit function. Then the laser light starts from the super-brightness semi-conductor laser amplifier 20 to the output coupler (〇u1: pUt ^ coupler) 50, where the reflection penetration ratio of the output coupler is 50/50. ^ In a preferred embodiment of the present invention, it further includes two <? Lenses 60a and 60b with a focal length f = 50min. The lens 60a will first converge to the output coupler 50, and then connect the lens 60a Re-collimate the laser light or lens 601 reflected from the output coupler 50 back to the super-brightness semiconductor moon laser amplifier 20 and re-collimate the laser light from the output coupler ^ 5 0 leaving the # cavity 1 〇. In a preferred embodiment of the invention, super brightness The distance between the two arms of the conductor laser amplifier 20 to the output coupler 50 and the grating 40 is equal to 1L = 1R. The length is corrected by the response frequency of the RF modulation, and the round-trip frequencies of the two arms are 803MHz, respectively. The round-trip frequency of the laser cavity is 401.5 MHz. The third circle illustrates the technical principle of the preferred embodiment of the present invention. Β In the preferred embodiment of the present invention, the DC bias current is greater than the critical current ( threshold

231-5287TWFl.ptc Page 7 V. Description of the invention (5) current) and transparent current (tranSparent current) are less than the critical current. That is, the jade dc &gt; Ith &gt; Itr must also satisfy that the RF modulation current must be greater than the difference between the DC bias current value and the transparent current value. That is, I nod> I dc _ Ϊ tr In a preferred embodiment of the present invention, when the wavelength is 83 nm, the transparent current is 36 mA and the critical current is 50 mA. When a DC bias current of 66 mA is applied, the difference between the DC bias current value and the transparent current value is 30 mA ′. Therefore, the modulation current must be greater than 30 mA. FIG. 4 is a timing diagram of a pulse laser for self-mixing mode locking of the present invention. In this architecture, when the pulse timing is 0, the first pulse laser is formed similar to the active mode locking. The ultra-brightness semiconductor laser amplifier's DC bias (D (: bias) current value is above the critical current value, and an RF modulation signal is applied. The RF modulation signal has the same frequency as each arm, which is 803Mifz When the modulation current is greater than the DC bias current, the first pulse laser is generated at the gain peak position of the RF modulation signal. In this architecture, when the pulse timing is 丨, the second pulse laser is similar: passive Formed by mode-locking. When the chirp modulation current is less than the transparent current, the super-brightness semiconductor laser amplifier is transformed into a modulation signal with a saturable absorber called modulation signal to generate a second pulse laser and Figure 5 shows The self-phase = variable power change diagram of the preferred embodiment of the present invention. When the DC bias current is input, the impulse: the second rate increases from-to 3 dBm. The half-width of the autocorrelation trace is reduced from 29PS to

Page 8 5. Description of the invention (6) ~ '1 5ps. When the DC bias current is 72mA, the modulation power is increased from _5dBm to OdBm, and the FWHM of the autocorrelation trace is reduced from 26ps to i6ps. The optimized RF modulation power varies with the DC bias current value. Fig. 6 is a half-width diagram of an autocorrelation trajectory pulse according to a preferred embodiment of the present invention. When the RF modulation frequency is less than -8dBm, the pulse laser is generated by the active mode-locking method and the FWHM of the autocorrelation trajectory is 34.1 6ps. When the rf modulation power is greater than -8 dBm, a pulse laser with self-mixing mode-locking starts to be produced. When the RF modulation power is increased to 0 dBm, the FWHM is quickly reduced to 14.29ps. When the RF modulation current is greater than the difference between the DC bias and the transparent current, the half-height width of the autocorrelation trajectory of the pulsed laser in this embodiment is more narrow than that of a conventional mode-locked laser. Figure 7 shows the application of a periodic The non-sine wave is the pulse laser timing diagram of this embodiment. In the present invention, as shown in FIG. 7, when the RF modulation frequency of self-mixing mode-locking is one third of the pulse laser frequency, pulse laser can also be generated. Therefore, as long as the frequency conversion rate of the modulation for the mode-locking by itself is 1 / n of the pulse laser frequency ', where η is an integer greater than or equal to 2, pulse_radiation can be generated. In the present invention, 'self-mixing mode-locking is similar to active mode-locking and passive mode-locking. The DC bias current and RF modulation frequency are different from the active mode locking; and the laser cavity does not have a saturable absorber in the place different from the passive mode locking. In the present invention, when the mode-locked RF modulation frequency is 1 / n of the pulse laser repetition frequency, η is an integer of 2 or more. When the modulation current of the semiconductor laser amplifier is at the peak of the gain, the pulsed laser starts from the semiconductor laser amplifier ’and returns to the amplifier through the laser cavity.

^ 465153 V. Description of the invention (7) The modulation current of the amplifier is just the valley of the gain. Using the modulation current larger than the difference between the transparent current and the DC bias, the semiconductor laser amplifier can be converted into a saturable absorber. At the peak of the gain of the RF modulation signal, the semiconductor laser amplifier generates a compressed pulsed laser as if it were actively mode-locked. When the gain and valley of the R-modulated signal is increased, the semiconductor laser amplifier generates a constricted pulse laser as if it were passively mode-locked. Self-mixing mode-locking combines active mode-locking and passive 鏔 ^; this effect produces short pulses with short pulses and no time jitter. At the same time, a self-mixing mode-locking semiconductor laser that does not require a saturable absorber and can use a single electrode, such as an edge-emitting semiconductor laser or a surface-emitting semiconductor laser. Because the self-mixing mode-locking uses single-electrode semiconductor radiation, electronic wiring can be reduced. In addition, the laser cavity can be a ring structure or a sacral structure and the laser cavity can be an external cavity laser cavity.

CaVlty) or monolithically integrated. Although the present invention has been better defined by the present invention, any person familiar with this god and scope, when making changes and viewing the scope of the patent application attached as described above, has the above examples, but it is not intended to be a craftsman. Does not deviate from the refined decoration of the present invention, so the definition of the protection scope of the present invention shall prevail "

Claims (1)

No. 89107430 VI. Please patent scope. This method is applicable to the method in which the DC bias and 1.— a method of self-mixing mode-locked laser generation—a semiconductor laser 'include the following features: applying a DC bias current to the semiconductor laser The historical current value is greater than the critical current value of the semiconductor laser to apply a -RF modulation signal to the semiconductor laser, and the second current value is greater than the DC current value and the semiconductor = F modulation power; the transparent current of Ding Shouyou from the spear τ The difference in value When the chirp modulation signal is a gain peak, the semiconductor laser pressure wall produces J laser, and then the RF modulation signal becomes a saturable absorber when the gain valley value is compressed, and compression generates a pulsed laser / conductor laser transition 2 . The method of self-mixing mode-locking to generate lightning as described in item 项 of the scope of the patent application, wherein the cycle frequency is 60 Hz and the pulse repetition frequency, where η is an integer greater than or equal to 2. 8. 3. The method of self-mixing mode-locking and generating mines as described in item 2 of the scope of patent application, wherein the RF modulation signal is a periodic wave. 4. The method of self-mixing mode-locking to generate mines as described in item 3 of the scope of patent application, wherein the periodic wave system is a periodic sine wave. 5. The method of self-mixing mode-locked generation of lightning as described in item 3 of the scope of patent application, wherein the periodic wave is a periodic pulse wave. 6. The method of self-mixing mode-locked laser generation as described in item 3 of the scope of patent application, wherein the periodic wave is a periodic non-sine wave. Page 11