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    1. What are the benefits of fiber-coupled diode lasers?

    The profile of common free output diode lasers is asymmetric (elliptic) Gaussian beam with a large divergence and nonuniform distribution. In most applications, it is necessary to shape and smooth the beamthere are two common shaping methods: optical lens shaping and fiber coupling shaping. Using lens could change the beam spot to rectangle but could not make it uniform , the space location for lens could not be removed flexibly. Using fibers, the output beam profile is rounded and uniform, the beam quality could improved, and the fiber coupling is an important means to realize flexible transmission which is popular in Medical, Industry areas. BWT Beijing has focused on fiber coupling diode lasers for over 15 years, and became the famous and professional manufacturers in international.



    2. What is the fiber coupling based on Single Emitter Diode Lasers?

    BWT‘s fiber coupled diode lasers can be divided into three categories: Single Emitter Diode Lasers, Mult-Single Emitter Diode Lasers, and Fiber Bundel Diode Lasers. Single Emitter Diode Lasers can provide the multi-wavelength covering from 405nm to 976nm, and the output power from 2mW to 10W. Multiple Single Emitter Diode Lasers are built upon the foundation of multi-emitter coupling technology to obtain the power reached to 200W and high brightness. Fiber bundel technology could bundel several diode lasers together and launch their beams into a single fiber via combiner, which could obtain the wavelength covering from 450nm to 1550nm and the power could reach to 300W.  Mult-Single Emitter Diode Lasers and Fiber Bundel Diode Lasers are the best options for high power diode lasers.



    3. What is the beam profile output from the fiber?

    Briefly, the beam output from the fiber is rounded with a certain divergence. The diameter of the beam is determined by fiber core, the divergence is relative with numerical aperture of fiber. The optical fibers are divided into single-mode and multi-mode, the numerical aperture (NA) is the sinusoidal value of maximum incident angle of total reflection a dimensionless number that characterizes the biggest range of angles over which the fiber can accept or emit light, it is usually between 0.15NA~0.22NA, 0.15NA is corresponding the half divergence of ~8°, and 0.22NA is corresponding the half divergence of ~12.5°. 



    4. What kinds of fiber connectors could be provided by BWT? What are the characteristics of each?

    BWT can provide the most of international standard fiber connectors, according to their structure, they mainly be divided into FC (FC/PC, FC/APC), ST, and SMA-905. Their appearances are shown in the figures as below. The FC connector is a fiber-optic connector with a threaded body and ceramic ferrule, the fiber end-face could be polished into plane (PC) or with 8° angle(APC), FC connectors’ benefit is the tight connection. The ST connector has a straight tip, the sides of the ceramic (which has a lower temperature coefficient of expansion than metal) tip are parallel. Its cable is pushed into the receiver, and the outer barrel is twisted to lock it into place, which is very easy to operate. SMA-905 connector also has a threaded body, and usually be processed by metal with the advantages of high temperature resistance and fast heat dissipation which is widely used in high power lasers. 



    5. What is the central wavelength and how to test it?

    Generally, the center wavelength in BWT website is corresponding to the center of full width at half maximum height of the spectrum measured at a certain temperature and power. The full width at half maximum height refers to the wavelength difference at both side of spectrum pulse corresponding to the half intensity of the peak. The center wavelength is mainly determined by the semiconductor material and would be shifted with the base plate temperature and operating current.



    6. How to choose the cooling method for diode lasers?

    The common cooling method is air cooling or water cooling. The required heat release for diode lasers could be calculated according to its output power and electric consumption. In general, single laser diode can be directly placed on the base plate with fans or TECs which is simple and easy to operate. For several high power diode lasers, water cooling plate is preferred, base plate with TECs and fans may be also available. 



    7. What accessories BWT can provide with diode lasers?

    Beside the high quality diode lasers, BWT also could offer rich kinds of accessories and complete solutions in lots of applications. Such as drivers, focused lens, collimators for scientific researches, solid settings for CTP printing, optical lens for illumination and imaging, and couplers, connectors for wide uses.

    For drivers, we could offer the customization services in below:

    A. Constant current drivers and constant output power drivers:

    Constant current drivers: output the constant current to control the diode lasers;

    Constant power drivers: adjust the current according to the feedback of Photo Diode to achieve the fixed output power.

    B. The optional functions and appearances

    Desktop version: the diode lasers, fiber coupling and heat dissipation are all integrated in a box. All the settings are displayed and adjustable on LCD panel.

    OEM version: it is convenient for users to integrate the laser systems inside the instruments.

    C. The optional operating modes(CW, pulsed and single pulsed mode)

    CW, pulsed or single pulsed mode is optional, the pulsed mode is achieved by TTL modulation single, the voltage of TTL single is between 0-5V. The output synchronizing signal form systems is very convenient for some applications. 



    8. What should be noted when operating the diode lasers?

    1. Laser safety

    Powerful laser radiation is dangerous, mainly for eyes and skin, don’t look at the laser beam straight, even wearing the laser goggles.

    2. Electrostatic protection

    The positive and negative pins must be shorted when the diode lasers are in transit or in storage. The Antistatic bracelet must be needed for the operator.

    3. Avoid the electrical surge

    A electrical surge is a sudden instantaneous electrical pulse, over high surge would break down PN junction and destroy the diode lasers. To avoid the electrical surge, the power supplier should be slowly started, and connected with diode lasers tightly. If the output power is adjustable via a potentiometer, it is better to use a current-limiting resistor in series with it.

    4. The connection between pins and driver

    For the operating current of >6A, please weld the pins to the wires of driver, the welding point should be close to the root of the pins as possible with the proper tension. To avoid damaging the diode lasers, please use the electric soldering iron with low power of <8W and temperature of <260℃,the welding time shall not over 10 seconds,at the same time, please offer the electrostatic protection.

    5. Cleaning

    Please clean the fiber end-face using the alcohol before turning on the laser to avoid reducing the output power or damaging the fiber. When the laser is not worked, please put the protected cap on the connector.

    6.The fiber bend radius 
    The maximum bend radius is recommended not less than 300 times of fiber cladding diameter.


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