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Patent Issued for Pulse Shaping Module and Generator for Use with a Pulsed Laser Oscillator

July 8, 2014

By a News Reporter-Staff News Editor at Information Technology Newsweekly -- Institut National d'Optique (Quebec, Quebec, CA) has been issued patent number 8761215, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Jacob, Michel (Quebec, CA); Deladurantaye, Pascal (St. Joseph de la Pointe-levy, CA); Taillon, Yves (Saint-Augustin de Desmaures, CA).

This patent was filed on December 7, 2011 and was published online on June 24, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Several industrial laser micromachining or material processing applications, such as metal engraving or memory link repair, require that laser light pulses with specific energy and temporal characteristics be precisely directed to a specific region of interest of a target material. For many applications, the rise-time and fall-time of such light pulses must be relatively short, preferably in the order of a few hundreds of picoseconds. It is also advantageous that the intensity profile of the light pulses be arbitrarily varied over the duration of the pulse, which itself varies depending on the application. By way of example, for memory link repair, the pulse duration is typically of a few tens of nanoseconds, while for metal engraving, it is typically of a few hundreds of nanoseconds. In this context, being able to generate light pulses with some capability for dynamically varying pulse durations with a temporal resolution at the nanosecond scale is certainly desirable. The process of generating short light pulses with controllable duration and controllable temporal intensity profile is commonly known in the art as 'pulse shaping'.

"Laser micromachining processes usually involve specifically tailored recipes consisting of a sequence of operations in which a large number of light pulses are successively impinged on a piece of material. Such recipes generally require that light pulses impinge on the target material for a given time interval during which the pulse repetition rate, the pulse shape, and sometimes the light wavelength can be dynamically switched among a predefined set of distinct combinations of these parameters. For example, the recipe may require that for a given time interval the optical output be simply turned off. The optical intensity may also be set to oscillate in what is commonly known in the art as a quasi-continuous wave (QCW) mode. A laser system operating in QCW mode typically emits a periodic signal oscillating at a frequency around 100 MHz with a duty cycle around 50%. Such functionalities are illustrated in FIG. 1, where the optical output OPTICAL_OUT, under the action of command signals QCW, EXT_TRIG, and SHAPEA/B, is switched between the above-mentioned modes.

"Furthermore, in many situations encountered in automated industrial manufacturing, a laser micromachining apparatus such as the one discussed above may need to operate in concert with other manufacturing equipment. For example, it starts or halts the machining of material pieces under remote control, or it may reply when it is remotely interrogated about the current statuses of its constituent lasers.

"From the discussion above, it can be seen that there is a need, at least in the context of industrial equipment, for combining some very low-level, agile and time-critical optical pulse shaping capabilities with electrical and optical power amplification, as well as high-level embedded intelligence for performing system housekeeping and managing communications with other equipment. Furthermore, such capabilities should be as low-cost as possible.

"The manner in which pulse shaping is performed may originate from electronic signals, either analog or digital, or from optical ones.

"U.S. Pat. No. 7,428,253 (MURISON et al.), entitled 'Method and system for a pulsed laser source emitting shaped optical waveforms' presents a wavelength-tunable pulsed laser source with optical pulse shaping based on a digital approach. MURISON mentions that the shaped waveform can originate from a digital pattern stored in memory on-board of a digital-to-analog converter (DAC). However, no embedded hardware implementation of digital pulse shaping is disclosed, except for the use of an off-the-shelf laboratory instrument such as the AWG2040 (tradename) waveform generator from Tektronix Inc., (Beaverton, Oreg.).

"U.S. Pat. No. 8,073,027 (DELADURANTAYE et al.), entitled 'Digital laser pulse shaping module and system' discloses a standalone embedded laser micromachining instrument based on digital pulse shaping. As shown in FIG. 2A (PRIOR ART), the instrument includes an input/output (I/O) port for interfacing with external equipment, a communication port for interfacing with a remote computer, a microcontroller for system housekeeping and control of pulse shaping, the digital pulse shaping sub-system and DAC, electrical power amplification and, finally, a laser oscillator for emission of the temporally-shaped output pulses. The electronic QCW/pulse shaping module shown in FIG. 2A is further detailed in FIG. 2B (PRIOR ART). It uses double-data rate (DDR) data output and is implemented preferably in a high-end Virtex-2 Pro FPGA (tradename) from Xilinx Inc., (San Jose, Calif.) in order to generate 10-bit pulse shapes with a typical temporal resolution of 2.5 ns. DELADURANTAYE also describes how the electronic pulse shaping system can be connected to several configurations or architectures of laser oscillators.

"U.S. Pat. No. 7,813,389 (PENG et al.), entitled 'Generating laser pulses of prescribed pulse shapes programmed through combination of separate electrical and optical modulators' discloses a pulse shaping approach based on superposing delayed analog electrical pulses. It also points out that a fully digital approach equivalent to their analog approach can be implemented using remote computer interfacing, programmed control, digital shaping, a DAC and power amplification. This is illustrated in FIG. 2C (PRIOR ART). PENG also suggests that the digital pulse shaping can be implemented in an FPGA such as the high-end Virtex-5 (tradename) from Xilinx Inc.

"The above-mentioned references teach that digital pulse shaping is preferably implemented using high-end, expensive FPGAs, therefore contributing significantly to the high cost of laser micromachining instruments. There is therefore a need for less expensive alternatives for implementing digital pulse shaping."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "In accordance with a first aspect of the present invention, there is provided a digital pulse shaping module for providing a digital waveform for use with a pulsed laser oscillator.

"The digital pulse shaping module first includes a waveform data generator for generating at least one N-bit word having a number N of bits. The at least one N-bit word is representative of the digital waveform. A serialiser is further provided. The serialiser receives the at least one N-bit words and outputs each bit thereof individually in a series of bits corresponding to the digital waveform. Finally, a delay module provides a fine delay in the outputting of the bits of the series by the serialiser corresponding to a number of bits smaller than N.

"In accordance with another aspect of the invention, there is provided a pulse shaping generator for providing a plurality of digital waveforms for use with a pulsed laser oscillator having an optical output. The pulse shaping generator includes a plurality of digital pulse shaping modules, each providing its respective digital waveform.

"Each digital pulse shaping module first includes a waveform data generator for generating at least one N-bit word having a number N of bits. The at least one N-bit word is representative of the respective digital waveform. Each digital pulse shaping module further includes a serialiser receiving the at least one N-bit word from the waveform data generator and outputting each bit thereof individually in a series of bits corresponding to the respective digital waveform. Finally, each digital pulse shaping module includes a delay module providing a fine delay in the outputting of the bits of the series by the serialiser corresponding to a number of bits smaller than N.

"In one embodiment, the digital waveform defines a pulse shape digital signal having a shape determinative of a shape of the optical output of the pulsed laser oscillator.

"In another embodiment, the digital waveform defines a gating digital signal having a binary structure selected to gate a specific component of the pulsed laser oscillator.

"In yet another embodiment, the digital waveform defines a synchronization digital signal set to be coincident with the optical output of the pulsed laser oscillator.

"It will be readily understood that the pulse shaping generator may include one or more waveform data modules, each associated with a digital waveform of one of the types above in any appropriate combination.

"In one particular embodiment of the invention, the pulse shaping generator may, for example, be embodied by an electronic digital platform which, under the action of a clock signal, a trigger signal and of other user-defined command signals, outputs control signals to a laser oscillator. Under the influence of such control signals, the laser oscillator may output either a QCW signal or a light pulse whose intensity is in some way proportional to the amplitude of an electrical signal defined by the digital waveform outputted by the pulse shape data generator.

"Other features and advantages of the present invention will be better understood upon a reading of the preferred embodiments thereof, with reference to the appended drawings."

For the URL and additional information on this patent, see: Jacob, Michel; Deladurantaye, Pascal; Taillon, Yves. Pulse Shaping Module and Generator for Use with a Pulsed Laser Oscillator. U.S. Patent Number 8761215, filed December 7, 2011, and published online on June 24, 2014. Patent URL:

Keywords for this news article include: Information Technology, Institut National d'Optique, Information and Data Generators.

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Source: Information Technology Newsweekly

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