Method and system for arbitrary optical pulse generation

A system, method, and apparatus for continuous seed laser pulses supplied to a CW pumped pre-amplifier and/or power-amplifier chain comprises an optical modulator configured to impress pulse signals on an optical signal, a waveform generator configured to establish a structure of the optical signal, and a keep-alive circuit that generates a continuous electrical pulse pattern provided to the optical modulator, wherein the system provides a continuous seed laser pulse structure.

TECHNICAL FIELD

Embodiments are generally related to the field of amplifiers. Embodiments are further related to the field of fiber amplifiers. Embodiments are further related to the field of optical amplifiers. Embodiments are also related to methods, systems, and devices for pump power supplied to amplifiers. Embodiments are further related to methods, systems, and devices for continuous seed laser pulses supplied to a CW pumped pre-amplifier and/or power-amplifier chain.

BACKGROUND

Amplifiers are a critical component of many electrical systems. Fiber amplifiers are a special type of optical amplifier that uses optical fiber as the gain medium. In some common examples, the gain medium can be doped glass fiber.

Fiber amplifiers are used in a number of applications. For example, in some cases, amplifiers are necessary in communication applications where signals need to be amplified because they travel a long distance. In other examples, fiber amplifiers can be used for high power application where power output, from hundreds of watts to thousands of watts, may be required. One such exemplary application is laser material processing.

While fiber amplifiers are useful, they also have certain limitations. Gain fiber needs to be pulsed when a laser output is desired. However, such pulsing can result in an output with a non-uniform amplitude. Further, when amps are pumped with high power, they need a continuous seed source or there is a possibility of failure. As such, on demand applications require a continuously pumped amplification system.

Accordingly, there is a need in the art for systems and methods that provide continuous seed laser pulses supplied to a CW pumped amplifier as further detailed in the embodiments disclosed herein.

BRIEF SUMMARY

It is, therefore, one aspect of the disclosed embodiments to provide a method, system, and apparatus for amplification.

It is another aspect of the disclosed embodiments to provide a method, system, and apparatus for providing fiber-based amplifier applications.

It is another aspect of the disclosed embodiments to provide methods, systems, and devices for pump power supplied to amplifiers.

It is yet another aspect of the disclosed embodiments to provide methods, systems, and devices for continuous seed laser pulses supplied to a CW pumped pre-amplifier and/or power-amplifier chain.

It is another aspect of the disclosed embodiments to provide a seed laser with a CW output and a Mach-Zehnder modulator (MZM) that creates a pulse train with a keep-alive circuit or arbitrary waveform generator (AWG) which can be input into the CW pumped fiber amplifier.

In the embodiments disclosed herein a system for supplying continuous seed laser pulses can comprise an optical modulator configured to impress pulse signals on an optical signal, a waveform generator configured to establish a structure of the optical signal, and a keep-alive circuit that generates a continuous electrical pulse pattern provided to the optical modulator wherein the system provides a continuous seed laser pulse structure. The system can include a synchronization circuit configured to synchronize the optical pulses to an external process. The system can further comprise a single frequency laser diode, wherein the single frequency laser diode outputs the optical signal.

In certain embodiment the system can comprise a computer system configured to implement non-transitory instruction media for controlling the waveform generator, generating a desired waveform. The waveform generator further generates a marker pulse provided to the keep-alive circuit.

In an embodiment the keep-alive circuit further comprises a crystal oscillator, a count-down and 1-shot circuit, a delay circuit configured to generate keep-alive pulses, and a driver circuit configured to generate at least one trigger.

In an embodiment the system further comprises a process trigger that synchronizes an output the system to a process. The system can provide a continuous seed laser pulse structure to an amplifier.

In an embodiment a pulse generation apparatus comprises a seed laser producing an optical signal, an optical modulator configured to impress pulse signals on the optical signal, a waveform generator configured to establish a structure of the optical signal, and a keep-alive circuit that generates a continuous electrical pulse pattern provided to the optical modulator wherein the system provides a continuous seed laser pulse structure. The pulse generation apparatus can further comprise a synchronization circuit configured to synchronize the optical pulses to an external process.

In certain embodiments, the seed laser further comprises a laser diode and an optical isolator.

In an embodiment the waveform generator further generates a marker pulse provided to the keep-alive circuit. In addition, in certain embodiments, the keep-alive circuit further comprises a crystal oscillator, a count-down and 1-shot circuit, a delay circuit configured to generate keep-alive pulses, and a driver circuit configured to generate at least one trigger. In certain embodiments the optical modulator comprises a Mach Zener Optical Modulator.

In an embodiment, the pulse generation apparatus further comprises a phase modulator and a radio frequency modulation module serves as an RF source for the phase modulator. The continuous seed laser pulse structure is provided to an amplifier.

In another embodiment, a method for pulse generation comprises producing an optical signal, imparting pulse signals on the optical signal with an optical modulator, structuring the optical signal with a waveform generator, generating a continuous electrical pulse pattern with a keep-alive circuit, the electrical pulse pattern being provided to the optical modulator, and providing a continuous seed laser pulse structure. In an embodiment the method for generation further comprises synchronizing the optical pulses to an external process with a synchronization circuit. In an embodiment the method for pulse generation further comprises generating a marker pulse and providing the marker pulse to the keep-alive circuit. The method for pulse generation can include providing the continuous seed laser pulse structure an amplifier.

DETAILED DESCRIPTION

The particular values and configurations discussed in the following non-limiting examples can be varied, and are cited merely to illustrate one or more embodiments and are not intended to limit the scope thereof.

A block diagram of a computer system100that executes programming for implementing parts of the methods and systems disclosed herein is shown inFIG. 1. A computing device in the form of a computer110configured to interface with controllers, peripheral devices, and other elements disclosed herein may include one or more processing units102, memory104, removable storage112, and non-removable storage114. Memory104may include volatile memory106and non-volatile memory108. Computer110may include or have access to a computing environment that includes a variety of transitory and non-transitory computer-readable media such as volatile memory106and non-volatile memory108, removable storage112and non-removable storage114. Computer storage includes, for example, random access memory (RAM), read only memory (ROM), erasable programmable read-only memory (EPROM) and electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD ROM), Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage, or other magnetic storage devices, or any other medium capable of storing computer-readable instructions as well as data including image data.

Computer110may include, or have access to, a computing environment that includes input116, output118, and a communication connection120. The computer may operate in a networked environment using a communication connection120to connect to one or more remote computers, remote sensors and/or controllers, detection devices, hand-held devices, multi-function devices (MFDs), speakers, mobile devices, tablet devices, mobile phones, Smartphone, or other such devices. The remote computer may also include a personal computer (PC), server, router, network PC, RFID enabled device, a peer device or other common network node, or the like. The communication connection may include a Local Area Network (LAN), a Wide Area Network (WAN), Bluetooth connection, or other networks. This functionality is described more fully in the description associated withFIG. 2below.

Output118is most commonly provided as a computer monitor, but may include any output device. Output118and/or input116may include a data collection apparatus associated with computer system100. In addition, input116, which commonly includes a computer keyboard and/or pointing device such as a computer mouse, computer track pad, or the like, allows a user to select and instruct computer system100. A user interface can be provided using output118and input116. Output118may function as a display for displaying data and information for a user, and for interactively displaying a graphical user interface (GUI)130.

Note that the term “GUI” generally refers to a type of environment that represents programs, files, options, and so forth by means of graphically displayed icons, menus, and dialog boxes on a computer monitor screen. A user can interact with the GUI to select and activate such options by directly touching the screen and/or pointing and clicking with a user input device116such as, for example, a pointing device such as a mouse, and/or with a keyboard. A particular item can function in the same manner to the user in all applications because the GUI provides standard software routines (e.g., module125) to handle these elements and report the user's actions. The GUI can further be used to display the electronic service image frames as discussed below.

Computer-readable instructions, for example, program module or node125, which can be representative of other modules or nodes described herein, are stored on a computer-readable medium and are executable by the processing unit102of computer110. Program module or node125may include a computer application. A hard drive, CD-ROM, RAM, Flash Memory, and a USB drive are just some examples of articles including a computer-readable medium.

FIG. 2depicts a graphical representation of a network of data-processing systems200in which aspects of the present invention may be implemented. Network data-processing system200can be a network of computers or other such devices, such as mobile phones, smart phones, sensors, controllers, speakers, tactile devices, and the like, in which embodiments of the present invention may be implemented. Note that the system200can be implemented in the context of a software module such as program module125. The system200includes a network202in communication with one or more clients210,212, and214. Network202may also be in communication with one or more devices204, servers206, and storage208. Network202is a medium that can be used to provide communications links between various devices and computers connected together within a networked data processing system such as computer system100. Network202may include connections such as wired communication links, wireless communication links of various types, and fiber optic cables. Network202can communicate with one or more servers206, one or more external devices such as device204, and a memory storage unit such as, for example, memory or database208. It should be understood that device204may be embodied as a circuit, detector device, controller, receiver, transmitter, transceiver, transducer, driver, signal generator, or other such device.

Computer system100can also be implemented as a server such as server206, depending upon design considerations. In the depicted example, server206provides data such as boot files, operating system images, applications, and application updates to clients210,212, and/or214. Clients210,212, and214and device204are clients to server206in this example. Network data-processing system200may include additional servers, clients, and other devices not shown. Specifically, clients may connect to any member of a network of servers, which provide equivalent content.

FIG. 3illustrates a software system300, which may be employed for directing the operation of the data-processing systems such as computer system100depicted inFIG. 1. Software application305, may be stored in memory104, on removable storage112, or on non-removable storage114shown inFIG. 1, and generally includes and/or is associated with a kernel or operating system310and a shell or interface315. One or more application programs, such as module(s) or node(s)125, may be “loaded” (i.e., transferred from removable storage114into the memory104) for execution by the data-processing system100. The data-processing system100can receive user commands and data through user interface315, which can include input116and output118, accessible by a user320. These inputs may then be acted upon by the computer system100in accordance with instructions from operating system310and/or software application305and any software module(s)125thereof.

The interface315(e.g., a graphical user interface130) can serve to display results, whereupon a user320may supply additional inputs or terminate a particular session. In some embodiments, operating system310and GUI130can be implemented in the context of a “windows” system. It can be appreciated, of course, that other types of systems are possible. For example, rather than a traditional “windows” system, other operation systems such as, for example, a real-time operating system (RTOS) more commonly employed in wireless systems may also be employed with respect to operating system310and interface315. The software application305can include, for example, module(s)125, which can include instructions for carrying out steps or logical operations such as those shown and described herein.

The following description is presented with respect to embodiments of the present invention, which can be embodied in the context of, or require the use of, a data-processing system such as computer system100, in conjunction with program module125, and data-processing system200and network202depicted inFIGS. 1-3. The present invention, however, is not limited to any particular application or any particular environment. Instead, those skilled in the art will find that the system and method of the present invention may be advantageously applied to a variety of system and application software including database management systems, word processors, and the like. Moreover, the present invention may be embodied on a variety of different platforms including Windows, Macintosh, UNIX, LINUX, Android, Arduino and the like. Therefore, the descriptions of the exemplary embodiments, which follow, are for purposes of illustration and not considered a limitation.

In the embodiments disclosed herein, a pulse (e.g. an optical pulse pattern) generation system can generate arbitrary pulse patterns in burst mode of operation (BMO), or pulse on demand (POD) mode of operation. This system can provide a continuous seed laser pulse structure to an amplifier, such as a CW pumped pre- and power-amplifier chain, such that when a set of laser pulses are requested in either mode, the gain fiber is at optimal gain. “Pumping,” as used in this context refers generally to energy transfer to a gain medium. The system can be synchronized to external processes and can generate triggers for pulse picking and laser diagnostics. It should be understood that the gain fiber can be co-pumped where the pump light and seed signal travel in the same direction, or it can be counter-pumped where the pump light and signal travel in opposite directions. The embodiments disclosed herein are not dependent on the direction of pump.

The system includes a “keep alive” circuit. The keep alive circuit is an electrical circuit whose output is sent to an electrical RF amplifier, whose output is input into a Mach Zener Optical Modulator (MZM) which modulates the CW seed source output automatically so that the amplifier does not fail while it waits for pulses of interest. When a pulse of interest is triggered the keep alive circuit automatically stops, and then restarts automatically after the pulse. This configuration allows the amplifier to operate properly so that it is ready at a high gain when a subsequent pulse is sent.

FIG. 4Aillustrates system400. The system400comprises a seed laser405that can serve as the initial laser source to be modulated, and optical isolator410. The function of the optical isolator410is to prevent optical signals from propagating backward into the seed laser and causing instabilities, oscillations, or damage. Such backward signals could come from reflections or instabilities in downstream amplifiers. In certain embodiments the laser405and optical isolator410assembly can comprise a narrow frequency single mode CW laser diode that produces a beam430.

Tap coupler425can be inserted in the beam path after the optical isolator410. The tap coupler425can provide an output beam431to a seed monitor495. The tap coupler425can remove only a small fraction of the beam. In an example embodiment, the tap coupler425can split the beam430at a ratio of 99:1, with the majority of the beam431progressing, and the minority of the beam being provided to the seed monitor495. Other beam splitting ratios may alternatively be used.

The beam431can then be subject to a phase modulator415, which can be embodied as an optical phase modulator. The phase modulator415can be connected to a radio frequency modulation module420, which serves as an RF source. The phase modulator415and RF source associated with radio frequency modulation module420are used to create frequency side-bands for shifting the non-linear Stimulated Brillouin Scattering (SBS) threshold above the operating point of the final CW pumped power amplifier. Specific frequencies and amplitudes are adjustable, and dependent on the specific power amplifier parameters.

The beam432is then incident on an optical modulator435that can comprise an amplitude modulator such as a Mach Zener Optical Modulator (MZM). In general, Mach-Zehnder modulators configured to split an input into two beams. A phase shift is induced in one of the beams as it passes along one path by applying a voltage. When the two beams are recombined, the phase difference between the two beams can be used for amplitude modulation.

The MZM Modulator435can include automatic bias control provided by MDC bias control470. The automatic MDC bias control470receives a signal from beam splitter475, that can siphon a small ratio of the beam433exiting the MZM435(e.g. at a ratio of 95:5, or other such ratio). The automatic bias control470can be used to maximize the contrast in the output of the MZM435between the states when the RF input is on/off between RF pulses. This provides contrast in the amplitude modulated optical signal output433of the MZM435.

The system400uses a keep-alive (KA) circuit440to generate a continuous electrical pulse pattern that is supplied to the optical modulator435. The MZM435can encode the electrical pulse pattern on the output of the beam433. The optical output (e.g. beam434) of the MZM435is used for input to a CW pumped fiber amplifier system (or other such system that uses an amplifier).

A desired pattern of laser pulses for amplification can be written to an arbitrary waveform generator445(AWG) which can be triggered by an external synchronization circuit450which locks the generation of the electrical pulse signal to any desired process. For example, in certain embodiments, the synchronization circuit450can lock the generation of optical laser pulses to an ion beam pulse structure. In other embodiments, other processes can serve as the desired process for generating the electrical pulse signal.

The AWG445provides an electrical pulse pattern triggered by process trigger485which is summed at455with a KA electrical pulse pattern provided by the keep alive circuit440. The process trigger485can comprise a trigger that synchronizes the output of the laser system to the process. The summed electrical pulse pattern is provided to an amplifier460and then used as input to the MZM435.FIG. 4Billustrates an enlarged view of certain aspects of the system400.

A key aspect of the embodiments disclosed herein is the “keep-alive” electrical circuit440. Aspects of the keep alive circuit440are illustrated inFIG. 5. The keep alive circuit440includes a crystal oscillator505operably connected to count-down and 1-shot circuits510, as well as delay circuits515which are configured to generate “keep-alive” pulses for the CW pumped amplifier, and driver circuits520connected to a combiner525to generate triggers for pulse picking via a Pockels cell. The Pockels cell receives a trigger from the keep-alive. The Pockels cell is used to act as a “gate” to open up and let the desired laser pulses through from the CW pump section to the pulse-pumped section. In the figures this is represented by the keep-alive pulse picker output. Diagnostic triggers for the amplifier system can also be provided.

FIG. 6illustrates an expansion of the single AWG embodiment, to an embodiment with 4 AWG's. Embodiments using multiple AWG's operate in essentially the same manner as disclosed with respect to a single AWG.FIG. 6shows a set of 4 multiplexed AWG generator modules. The area within the dashed line is functionally the same as a single AWG445.

Each AWG module can contain a completely different, and independent, waveform. The AWG to be selected and waveform to be sent to the modulator and amplifier system is determined by a 2-bit address which routes the trigger and output via a de-multiplexer and two multiplexers.

The output of the process trigger is used to trigger one of the AWG modules illustrated inFIG. 6. The specific AWG module that is to be triggered is selected by the de-multiplexer on the left by setting the 2-bit address (i.e. s1, s2). These would be, for example, “00” for the first AWG, “01” for the second AWG, “10” for the third AWG, and “11” for the fourth AWG.

Once the address is set and a trigger from the process trigger occurs, the specific AWG, as determined by the address lines, starts to play a pre-loaded waveform table. Each of the outputs from the AWG, the marker and the waveform, are directed to different multiplexers.

The same digital address that selects the channel on the de-multiplexer also selects the same channel on both of the output multiplexers. The operation from this point is exactly similar to that of a single AWG.

To force the electrical pulse patterns from the AWG circuit445and KA circuit440to be mutually exclusive in time, the AWG445additionally generates a set of “marker” pulses465during the AWG electrical pattern which are used to “clamp” the output of the KA circuit440electrical pulses. Thus, only the desired waveform from the AWG445can be input into the MZM435.

Each marker pulse465starts a count-down of a specific duration, and if another marker pulse does not renew the count-down within the specified duration, the KA oscillator output is un-clamped and resumes providing continuous seed pulses to the CW pumped amplifier system.

The output beam433from the MZM435can be subject to a second tap coupler480. The tap coupler480provides a small ratio (e.g. 99:1, or other such ratio) of the beam to a modulator monitor496. The bulk of the beam434can be provided as modulator output490to a CW pumped pre-amplifier and/or power-amplifier chain.

The arbitrary waveform generator445defines the temporal and amplitude structure of the laser pulses supplied by the MZM output431. The waveform generator445can also generate the “marker” pulses465, as illustrated herein, that can be used by the “keep-alive” circuit440to clamp its output.

It should be understood that software and/or software modules associated with computer system100, can be used to generate a waveform including an arbitrary waveform as required in various embodiments disclosed herein. Thus, the AWG can be operably connected to a computer system100, or other such device. The software used for the generation of the desired pulse pattern allows for control of the timing of the waveform after the trigger, the number of bursts, the number of pulses during each burst, the separation between bursts, temporal width, and amplitude of each pulse within the waveform. The software automatically includes the “marker” pulse(s) for control of the KA during the defined pulse pattern.

Exemplary timing of the marker pulses705, keep-alive pulses710, pulse picker gate715, and trigger720are provided in chart700, illustrated inFIG. 7. The region725following keep-alive pulses710contains the arbitrary pulse pattern.

FIG. 8illustrates a method800wherein a synchronization circuit provides the ability to synchronize optical pulses to an external process by providing a synchronized trigger for the arbitrary waveform generator, in accordance with the disclosed embodiments. The method starts at805.

In certain embodiments a crystal oscillator keep-alive (KA) circuit can generate a continuous electrical pulse pattern that is supplied to a Mach-Zehnder Optical Modulator (MZM) as shown at step810. This MZM encodes the electrical pulse pattern on the output of a wavelength stabilized CW laser diode as shown at step815. At step820, the optical output of the MZM can be used for input to the CW pumped fiber amplifier system. A desired pattern of laser pulses for amplification can be written to an AWG to be triggered by an external synchronization circuit which locks the generation of the electrical pulse signal to any desired process, as shown at step825. This locks the generation of the optical laser pulses to the process (e.g. the ion beam pulse structure).

As shown at830the AWG provides the electrical pulse pattern, which is summed with the KA electrical pulse pattern for input into the MZM. To force the electrical pulse patterns from the AWG and KA circuits to be mutually exclusive in time, the AWG additionally generates a set of “marker” pulses during the AWG electrical pattern which are used to “clamp” the output of the KA electrical pulses, thus allowing the AWG pulses to pass onto the MZM as shown at step835. As such, only the desired waveform from the AWG are allowed to be input into the MZM. Each marker pulse starts a countdown of a specific duration and if another marker pulse does not renew the countdown within the specified duration, the KA oscillator output is un-clamped and resumes, to provide continuous seed pulses to the CW pumped amplifier system as shown at840. The method ends at845.

Based on the foregoing, it can be appreciated that a number of embodiments, preferred and alternative, are disclosed herein. For example, in an embodiment, a system comprises an optical modulator configured to impress pulse signals on an optical signal, a waveform generator configured to establish a structure of the optical signal, and a keep-alive circuit that generates a continuous electrical pulse pattern provided to the optical modulator wherein the system provides a continuous seed laser pulse structure.

In an embodiment, the system further comprises a synchronization circuit configured to synchronize the optical pulses to an external process. In an embodiment, the system further comprises a single frequency laser diode, wherein the single frequency laser diode outputs the optical signal.

In an embodiment, the system further comprises a computer system configured to implement non-transitory instruction media for controlling the waveform generator, generating a desired waveform.

In an embodiment the waveform generator further generates a marker pulse provided to the keep-alive circuit.

In an embodiment, the keep-alive circuit further comprises a crystal oscillator, a count-down and 1-shot circuit, a delay circuit configured to generate keep-alive pulses, and a driver circuit configured to generate at least one trigger. In an embodiment, the trigger comprises a process trigger that synchronizes an output the system to a process. In an embodiment, the continuous seed laser pulse structure is provided to an amplifier.

In an embodiment, a pulse generation apparatus comprises a seed laser producing an optical signal, an optical modulator configured to impress pulse signals on the optical signal, a waveform generator configured to establish a structure of the optical signal, and a keep-alive circuit that generates a continuous electrical pulse pattern provided to the optical modulator wherein the system provides a continuous seed laser pulse structure.

In an embodiment, the pulse generation apparatus further comprises a synchronization circuit configured to synchronize the optical pulses to an external process.

In an embodiment, the seed laser further comprises a laser diode and an optical isolator.

In an embodiment, the pulse generation apparatus further comprises waveform generator further generates a marker pulse provided to the keep-alive circuit.

In an embodiment, the keep-alive circuit further comprises a crystal oscillator, a count-down and 1-shot circuit, a delay circuit configured to generate keep-alive pulses, and a driver circuit configured to generate at least one trigger.

In an embodiment, the optical modulator comprises a Mach Zener Optical Modulator.

In an embodiment, the pulse generation apparatus further comprises a phase modulator and a radio frequency modulation module serves as an RF source for the phase modulator.

In an embodiment, the continuous seed laser pulse structure is provided to an amplifier.

In an embodiment, a method for pulse generation comprises producing an optical signal, imparting pulse signals on the optical signal with an optical modulator, structuring the optical signal with a waveform generator, generating a continuous electrical pulse pattern with a keep-alive circuit, the electrical pulse patter being provided to the optical modulator, and providing a continuous seed laser pulse structure.

In an embodiment, the method for pulse generation further comprises synchronizing the optical pulses to an external process with a synchronization circuit. In an embodiment, the method for pulse generation further comprises generating a marker pulse and providing the marker pulse to the keep-alive circuit. In an embodiment, the method for pulse generation further comprises providing the continuous seed laser pulse structure an amplifier.