Compact module for complementary-channel terahertz pulse slicing

Abstract

A pulse synthesizer generating pulses by swapping electromagnetic radiation between two channels using a sequence of switches activated with various delay times. In one embodiment, the synthesizer comprises a slicing module is capable of slicing flexible pulse durations from a wide range (240-500GHz) of frequencies, using commercially available mirrors to generate pulses of arbitrary length (> 1 ns ) from a cw or quasi-cw THz beam. It is also modular and stackable, allowing pulses to be created by simply stacking boxes in series, and returns the additive channel and its complement, allowing concurrent measurement of beam parameters. The capabilities demonstrated here make the pulse slicer highly flexible and useful for a broad range of spectroscopic applications including FEL or gyrotron pulsed ESR and DNP.

Description

[0001] COMPACT MODULE FOR COMPLEMENTARY-CHANNEL TERAHERTZ PULSE SLICING CROSS REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. Section 119(e) of U.S. Provisional Application No.63 / 591,828 filed October 20, 2023, by Brad Price, Antonin Sojka, Nikolay Agladze, and Mark Sherwin, entitled “COMPACT MODULE FOR COMPLEMENTARY-CHANNEL TERAHERTZ PULSE SLICING,” attorney’s docket number 30794.0845USP1, which application is incorporated by reference herein. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT This invention was made with Government support under Grant No. DMR 2117994, awarded by the National Science Foundation (NSF). The Government has certain rights in the invention. BACKGROUND OF THE INVENTION 1. Field of the Invention. The present disclosure relates methods and systems for slicing electromagnetic radiation. 2. Description of the Related Art. High power, narrow band terahertz (0.1–10 THz) waves are crucial for heating plasmas in fusion reactors, wireless communications with ultra-high data rates, radar with mm-range spatial resolution, electron beam accelerators, and coherent manipulation of quantum states (amongst other applications). For all of these applications, complex THz waveforms are desirable; traveling- wave-tube and gyrotron amplifiers are under development to create such waveforms, but scaling them to high frequencies is challenging. What is needed, then, are improved systems for generating pulses of terahertz (THz) radiation. The present disclosure satisfies this need. SUMMARY OF THE INVENTION The present invention is a pulse slicer which can be used to slice electromagnetic radiation at a variety of frequencies (e.g., but not limited to, microwave to infrared frequencies at 100 GHz to 50 THz, but demonstrated here for slicing electromagnetic radiation at terahertz frequencies. The system comprises identical modules with two inputs and two outputs allowing stacking of modules combining two outputs of each module with two inputs of the next module. In the demonstrated embodiment, the quasioptical modular design incorporates a laser-driven silicon switch at Brewster's angle to incoming terahertz radiation to limit undesired reflections in the "off" state and ensure that terahertz power is only transmitted when the switch is "on". Further, an "off" switch ensures that no power is leaked after the pulse and that the switching profile is sharp. The slicer has a primary output with the desired pulse sequence and a secondary output that returns the complement of the first output. An additional feature of the pulse slicer is splitting of the laser pulses generating multiple pulses 2, 3, etc. and directing a part of the radiation to the preceding switches, maintaining a high reflection in the ON state thus overcoming limitations imposed on times between pulses due to the carriers relaxation in the switch material. This design will enable more complex kW-power pulse sequences than existing pulse slicers for free electron laser or gyrotron-powered pulsed ESR and has potential applications for pulsed DNP. The results presented herein show the pulse slicer is capable of generating flexible pulse durations (e.g., >1 ns) with customizable start and stop timings over a broad range of frequencies (>240 GHz). In various examples, the slicer can be implemented with a small footprint (48x72x162 mm) and small insertion loss (1.2 dB at 320 GHz) as well as high switching efficiency (>65%) allowing pulse slicers to be stacked to create complex pulse sequences. BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the drawings in which like reference numbers represent corresponding parts throughout: FIG.1. Modular pulse slicer optics. Parabolic mirrors ( f = 50.8 mm, 35-644, Edmund Optics, NJ, USA) focus collimated incoming THz waves (pink) onto a 50.8 mm diameter silicon wafer at Brewster’s angle. Depending on switch state, the THz waves are either transmitted (pink) or reflected (blue) at the first switch. Similarly, pulses are either transmitted (pink and blue) or reflected (black) by the second switch. As shown in the timing diagram (bottom), during slicing, pink is output first, then blue, and finally black. A pulse (∼3.8 mm beam diameter) from a 532 nm diode- pumped laser (VRN20-50-G, Lumibird, USA) incident on the silicon wafer (in this figure, illumination is from the right-hand side of both wafers) promotes electrons into the conduction band and switches silicon from transmissive-to- reflective for THz for the duration of the lifetime of the carriers. Eight parabolic mirrors and two silicon wafers (as shown) constitute one pulse slicing module. FIG.2. Modular pulse slicer assembly. The arrangement of mirrors, silicon wafers, and Gaussian sub-mm beams (as depicted in Fig.1) is integrated within a pair of pulse slicer modules, highlighted by red out- lines. The overall assembly involves dual 25 mJ lasers emitting a 9 ns 532 nm pulse, 3.8 mm in diameter, that is expanded beyond the focal length (9.5 mm) of a spherical concave mirror to fully cover the face of the silicon wafer (and incident THz wave Gaussian beam) inside each box. The pulse slicer box precisely aligns four parabolic mirrors with the central silicon wafer at Brewster’s angle. The pulse slicer assembly’s stackable nature is visually depicted in a black and white illustration – the configuration shown would be used to make two sharp pulses from a quasi-cw high power beam. FIG.3. Pulses sliced from cw sub-mm Gaussian beam. The delay between on and off switches for each pulse length is shown in the legend. Peak power is achieved down to approximately 10 ns pulses. Below 10 ns, the pulse length of the laser (∼ 9 ns, shown by the gray vertical bar) does not allow for the full 25 mJ to be deposited onto the wafer before the pulse is switched off. The deviations from square temporal profiles are due to the AC coupling of the detector and the fine structure of each pulse is likely due to standing waves in the quasioptical test bench (period of 2.2 ns). Experiments were repeated at 20 Hz and averaged 13× at each set of laser timings. FIG.4. Sliced pulses of 25 and 100 ns . Pulses shorter than 25 ns , while possible, suffer significant distortion due to convolution with the 20 ns probe pulse.Experiments were repeated at 20 Hz and averaged 13 × at each delay. (a) Additivechannel that makes up the sequence of pulses. Power is normalized to the transmitted power with both lasers off. (b) Subtractive channel that subsequent pulses are sliced from. Power is normalized to the transmitted power with both lasers off. Data was recorded by sweeping 20 ns THz pulses through the laser timing. The recorded data is a convolution of the slice timing with the probe pulse and results in a less sharp recorded profile than that shown in Fig.3. Effect of 320 GHz pulse convolution with slicing profile. (c) Convolution (green) of pulses (blue) with additive slicing profile (red). (d) Convolution (green) of pulses (blue) with subtractive slicing profile (orange). As seen here, convolution reduces the sharpness of the slicing profile and can reduce the modulation depth for short slicing times. FIG.5. Simulated additive channel output of three stacked modularassemblies. The peak power of the ^^^^th pulse, ^^^^ is given by ^^^^ 2^^^^−1^^^^ ^^^^ = ^^^^0^^^^ , where ^^^^0is the initial input power and ^^^^ is the peak reflectance of a single silicon wafer. Gray represents an initial high power THz beam and green represents the resulting additive channel output by the pulse slicing assemblies. FIG.6. Reflectance of a single silicon wafer after excitation by a25 mJ, 532 nm laser pulse. Power in the additive channel was collected by sweepinga 20 ns THz pulse in time across the laser pulse timing and integrating the total power of the THz pulse. Reflectance (solid blue) was calculated by dividing the power detected in the additive channel by the power in the subtractive channel when theswitch was not activated. Experiments were repeated at 20 Hz and averaged 13 × at each delay. (Inset) Reflectance between 0.2 and 0.5^^^^ s. An example timing for an echo-detected inversion recovery pulsed ESR sequence is shown by the red vertical bars. FIG.7a. Zemax (version Nov.12, 2005) simulations of insertion loss and spatial mode filtering through the test setup ( 5 pairs of offaxis parabolic mirrors;Edmund Optics 35 − 644 ). The fundamental, TEM00 mode (shown in blue)experiences approximately 1 dB of insertion loss across the frequencies of interest, while TEM11(green) and TEM22(orange) experience 3 dB and 4 dB , respectively. Simulation frequencies match those in Fig.7: 240, 329,461,661GHz. The beam waist used for this calculation was 5.7915 mm3. FIG.7b. Simulation of the beam waist through a pulse slicer module at a selection of frequencies commonly used for dynamic nuclear polarization (DNP). As shown, frequencies of 240 GHz and above will propagate through the quasioptics with few losses. Lower frequencies, due to additional divergence, will partially fall outside the diameter of the silicon wafer. A larger wafer would be required to use thisdesign at frequencies < 240GHz. Vertical gray lines represent the position and inputdiameter of the parabolic mirrors, the angled green line represents the silicon wafer, and the red, blue, yellow, and black lines represent a circle that encloses 99% of theGaussian beam energy at 240 GHz , as well as DNP frequencies 329GHz, 461GHz,and 661 GHz respectively43. FIG.8. Pulse slicing simulation of 6 modules. Taking 100% of the input power to be in the subtractive channel, the output power of the subtractive (blue) andadditive (green) channels is shown as a function of time. For this simulation, ^^^^ =1,^^^^ = and laser timings are 50, 150,300,500,750, and 1050 ns .FIG.9 The slicer module silicon exchange mechanism. Two slicer boxes are interconnected and aligned using a silicon wafer exchange system connected to a stepper motor. This mechanism accommodates up to four wafers: two within the boxes and two positioned between them. Additionally, spring-loaded wafer holders in each box allow for precision tuning of wafer position via set screws. FIG.10. CNC-machined pulse-slicing box. Readily available parabolic mirrors (35-644, Edmund Optics, NJ, USA) focus collimated incoming mm waves onto a 50.8 mm diameter silicon wafer at Brewster's angle. All metallic components were machined from high-precision 6.35 mm plates (3511T115, McMasterCarr, IL, USA). The parts were designed to be symmetric so that only 3 distinct parts were required for the design, which simplified the manufacturing process. Plastic components (the wafer holder and carousel) were 3D-printed for rapid prototyping and flexible, scratch-free mounting of the Si wafers (for 320 GHz , this thickness usedwas 279 ± 25^^^^ m, wafers provided by Virginia Semiconductor, VA, USA). Thewafer-holder carousel features springs an adjustable screw in order to adjust the wafer position to ensure the beam is nominally at Brewster's angle and intra-module alignment is optimized. Fig.11. Flowchart illustrating a method of making a pulse synthesizer and operating the pulse synthesizer. Fig.12. Schematic of a pulse synthesizer according to one or more embodiments. Fig.13. Example hardware environment. Fig.14. Example network environment. DETAILED DESCRIPTION OF THE INVENTION In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Technical Description Fig.1 illustrates a pair of slicer modules connected for pulse generation. As illustrated in Fig.1, each slicer module comprises a medium comprising a property that can be modulated to switch the medium between a transmissive state and a reflective state; control inputs for receiving control signals for modulating the property to switch between the transmissive state and the reflective state at a region of the medium; a first input and a second input; and a first output and a second output. Each of the inputs is interchangeable or equivalent in the sense that the module will operate when electromagnetic radiation is inputted into either the first input or the second input. A first path defined as coupling the first input to the first output when the switch is not activated, and a second path is defined as coupling the second input to the second output when the switch is not activated. Fig.1 illustrates the first path and the second path intersect at the region of the medium receiving the control signals so that activation of the switch by the control signals performs a swap of electromagnetic radiation (inputted at either the first input or the second input) between the two paths, redirecting: (i) electromagnetic radiation from the first path to the second path; and (ii) electromagnetic radiation from the second path to the first path . Fig.1 further illustrates an example wherein a pair of the modules are connected so that the first output of the first module is connected to the first input of the second module, and the second output of the first module is connected to the second input of the second module; During operation, the switch in the second module is activated later than the switch in the first module so that a combination of the swap in the first module and the swap in the second module outputs a pulse at the second output the second module and a complementary pattern of the electromagnetic radiation at the first output of the second module when the electromagnetic radiation is inputted to the first input of the first module. In typical embodiments, a controller controls application of the control signals to control timing of the transmissive state and the reflective state for the electromagnetic radiation inputted onto the medium. For the working embodiment demonstrated herein, a laser system (laser diodes) couples the control signals comprising a laser beam. The laser beam is input onto the medium to modulate the property in the region of the medium on which the electromagnetic radiation is incident. Working Example 1. System Fig. 1 demonstrates the operation of a pair of pulse slicing modules 100 for slicing THz radiation, wherein one of the first path 116 or second path18 comprises a subtractive channel and the other of the paths comprises an additive channel. The input electromagnetic radiation THz beam (116a) is reflected by the first parabolic mirror and subsequently passes through the first medium (silicon wafer 102) into the subtractive channel output. Upon activation on a region 106 of the first wafer using control signal to the first module (laser beam from Laser-1), the input beam is reflected by the front surface of the silicon wafer and directed into the additive channel (118b), while the subtractive channel is turned off. Both channels are then collimated using a parabolic mirror, producing two beams that match the original input beam’s size and profile. These beams are used as inputs for a second set of parabolic mirrors, and the entire process is repeated. When Laser-2 activates the second wafer, the beam in the additive channel is directed into the subtractive channel (now black), which turns off the additive channel and leaves a sharp pulse 126 behind (see Fig. 1, bottom). Additional pulses can be generated using the output 128 of the subtractive channel as the input for subsequent modules, as illustrated in Fig.2. Fig.2 illustrates a pulse slicer in a working embodiment, comprising two diode-pumped lasers (VRN20-50-G, Lumibird Photonics, France) that are used to drive the silicon switches. These lasers, in conjunction with the pulse boxes and optics for laser beam expansion, are securely mounted onto a base plate. Both green laser beams are reflected and expanded by a 9.5 mm focal length concave spherical mirror (CM127-010-G01, Thorlabs, USA). Beam expansion ensures the precise overlap of microwave and laser beams onto the silicon wafer's surface. All components are mounted to a portable baseplate that connects the lasers and 532 nm components to CNC-milled aluminum housing (indicated in red) that was designed to fix all quasioptical components in place and minimize positioning errors. This assembly also incorporates a wafer exchange system, which facilitates insertion of silicon wafers of the correct wafer thickness for a given frequency. Each pulse slicer assembly ( 2 lasers, 2 wafers, 16 off-axis parabolic mirrors) is designed to generate a single pulse. Fig.2 shows two stacked assemblies, as would be used to generate two pulses from an input beam. Because of its small footprint, additional modules could be stacked to generate more than two pulses, and a protective enclosure can easily be employed to increase eye safety and reduce scattered laser light. The capabilities of complementary-channel modular pulse slicer design weredemonstrated using a 320GHz(∼ 100^^^^ W) source-and-detector test setup (VDI-0027source, Virginia Diodes, Inc., Charlottesville, VA; AC-coupled quasioptical detector,3DL 12C LS2500 A2, ACST gmbH, Germany) and two 279 ± 25^^^^ m float-zone,high-resistivity, < 111 > undoped silicon wafers (Virginia Semiconductor, VA,USA). Pulse slicing experiments were done in either " cw " mode, where a pulse was directly sliced from a low-power cw beam, or "stepped" (convolutional) mode, where a 20 ns 320 GHz pulse was stepped through the slicing timing. 2. Characterization results a. Continuous wave pulse slicing The slicer can be used to slice pulsed or continuous wave electromagnetic radiation. Fig. 3 demonstrates sliced pulses with durations between 1 and 50 ns generated by two lasers and two wafers from continuous wave input THz electromagnetic radiation. The rise and fall times of these edges are currently limited by the 9 ns pulse length of the laser used (depicted in gray in Fig. 3). Shorter pulses with faster rise and fall times could be achieved by activating the silicon switch with picosecond (ps) or even femtosecond (fs) laser pulses. Recorded pulse profiles are distorted due to the AC-coupling of the detector, but the detector’s fast response (4 MHz-4 GHz bandwidth) was able to capture the slopes of the rising and falling edges. b. Convolutional pulse slicing To avoid the limitations of the AC-coupled quasioptical detector, we have also measured transfer function of the modular pulse slicer by stepping the timing of a 20 ns 320 GHz close-to-square probe pulse with respect to the timing of laser pulses 1 and 2 (see Fig.4a,b). This method returns a convolution of the transfer function and probe pulse with rising and falling edges less steep than a pulse sliced from a cw beam (simulation of the convolution effect is shown in Fig.4c showing a convolution of the slicing profile (which is sharp) and an approximately square pulse, meaning that the recorded profile is less sharp than the true sliced pulse.. Fig.4 further shows the additive and subtractive outputs of complementary channel pulse slicing, and highlights the temporal flexibility of the modular design. Fig.4a shows 25 ns and 100 ns pulses with conversion efficiencies around 70%. Fig. 4b shows the power returned by the complementary subtractive channel; the power in this channel can be used to create additional pulses by stacking modules. It is important to note that the maximum power of each subsequent pulse ^^^^ is given by^^^^^^^^ = ^^^^0^^^^2^^^^−1, where ^^^^ is the peak reflectivity of the wafer. The simulated additivechannel output of three stacked modular assemblies is shown in Fig.5 and the output of the last module's subtractive channel may also be used to measure beam parameters. c. Single-laser reflectivity The modular pulse slicer relies on the long recombination time of photo- excited electrons and holes in silicon. As shown in Fig.4, for the wafers that we are using, the reflectivity remains substantial for 10^^^^ s, and over the sub- ^^^^s duration of atypical ESR pulse sequence ( < 1^^^^ s, shown in red in Fig. 6), decays by < 10%. Theshape of the decay depends on the surface recombination, the Auger lifetime, carrier diffusion, and the Shockley-Read-Hall recombination due to impurities35,41. Recombination due to surfaces and impurities may be mitigated in the future adapting methods and materials developed for silicon photovoltaics42. d. Insertion Loss The insertion loss of the subtractive channel of the pulse slicer was measured to be 1.2 dB at 320 GHz . This loss can be attributed to two factors: (1) imperfect quasioptical coupling that may be present due to alignment of optical components and (2) spatial filtering of the THz beam by the pairs of off-axis parabolic mirrors; the attenuation due to the beam being clipped by the parabolic mirrors increases with increasing mode order. It is estimated that at 320 GHz , the attenuation for theTEM00, TEM11, and TEM22 modes are 0.8,2.9, 3.6 dB , respectively (see Fig. 7a forsimulation results at 240GHz, 320GHz, and select DNP frequencies). The insertionloss of the additive channel is dominated by the peak reflectance of the semiconducting wafer, with additional losses from imperfect quasioptical coupling and spatial filtering, comparable to those of the subtractive channel. Fig.7b depicts a simulation of a diameter that encloses 99% of the encircled energy for a selection of DNP frequencies and demonstrates that frequencies higher than 240 GHz will propagate without issue. Below 240 GHz , some additive channel power will be lost because the diameter enclosing 99% encircled energy of the Gaussian profile falls outside the diameter of the silicon wafer. Below 150 GHz , the circle enclosing 99% encircled beam energy also falls outside the input diameter of the parabolic mirrors. d. Spatial mode Filtering The pairs of parabolic mirrors attenuate non TEM00modes more strongly than TEM00and result in a spatial filtering effect that can "clean-up" beam modes when transmitted through the modular pulse slicer. Higher-order modes diverge more quickly than TEM00and are clipped by quasioptical elements more strongly. Fig.7a demonstrates this effect for three low-order modes at select frequencies that are compatible with DNP-NMR. e. Simulation of pulse slicing using matrix formulation Using an input vector containing relative field strengths in the subtractive and additive channels, an individual pulse slicer module can be represented as a 2-by-2 matrix, where ^^^^^^^^and ^^^^^^^^are the initial and final powers, and ^^^^^^^^and ^^^^^^^^are the subtractive and additive channels. For an individual laser (and module) timing, ^^^^^^^^, each element can be represented with a simple expression, where ^^^^ is the transmission coefficient of an unactivated silicon wafer, ^^^^ is the reflection coefficient of the silicon wafer as a function of time after laser excitation ^^^^^^^^, and ^^^^ is the Heaviside step function. Since ^^^^ only represents a single module, onepulse can be sliced by two modules�^^^^^^^^ = ^^^^2^^^^^^^^�, and three pulses can be sliced by sixmodules ( ^^^^ 6^^^^ = ^^^^ ^^^^^^^^�.A simulation with 100% of the input power into the subtractive channel,taking laser timings of 50,150,300,500,750, and1050 ns is shown inFig. 8�^^^^^^^^=0 = √0.7 was chosen because the peak power obtained in experiments wasapproximately 70% ). Example Wafer Exchange Mechanism Precisely tuning the wafer thickness for specific frequencies leads to destructive interference between front- and backsurface reflections from the wafer, and thereby minimizes undesirable reflection of rays not at Brewster’s angle. Therefore, in order to achieve optimal performance across a wide range of frequencies, the silicon wafers need to be replaceable. Our design incorporates an automated solution for this process through a silicon exchange mechanism (see Fig.9) that can automatically switch between two pairs of wafers of different thicknesses. Positioned between two pulse boxes, this mechanism not only facilitates wafer replacement but also ensures effective microwave coupling between pairs of parabolic mirrors via an adjustable set screw; each wafer’s position can be finely adjusted to ensure its precise alignment within the microwave beam waist. The modules' housing, shown in Fig.10, was machined from high-precision 6.35 mm - thick aluminum plates (3511T115, McMaster-Carr, IL, USA). Accompanying mirrors were purchased from Edmund optics (35-644, Edmund Optics, NJ, USA). Advantages and Improvements Advantages of the pulse slicer module described herein include, but are not limited to, the following. • compactness; • modular assembly; • generation of multiple pulses; • high on-off contrast; • low insertion loss; • spatial mode filtering (returns fundamental Gaussian mode); • electronically controlled customizable pulse length; • subsequent pulses are sliced from complementary output; complementary beam can be used for beam analysis; • broad-band; • inter-pulse phase control; • simple construction; • inexpensive to manufacture. More specifically, the results demonstrate the feasibility of a frequency-agilepulse slicing module for slicing short ( > 1 ns ) pulses from a cw or quasi-cw THzsource. The modular design vastly reduces the required space compared to the mostsophisticated previous design 34 and can slice pulses with a 48 × 72 mm footprintrather than a large fraction of a 1.2 × 2.4 m optical table. The modules can also bestacked together to slice as many pulses as necessary, which will enable three-pulse echo-detected inversion recovery ESR experiments, for example. The timings of the pulse edges are set entirely electronically and do not require a physical delay stage that caps the maximum pulse length. Additionally, this modular design requires no custom optics and can be almost entirely manufactured with three CNC-milled parts. Process Steps Fig.11 is a flowchart illustrating a method of synthesizing pulses, comprising the following steps. Block 1100 represents obtaining, assembling, or fabricating one or more pairs of switches comprising a first switch and a second switch coupling a first pathway and a second pathway, each of the switches comprising a first input; a second input; a first output; a second output; a first output and a second output; wherein the first input is coupled to the first output and the second input is coupled to the second output when the switch is not activated; and wherein: the first output of the first switch is connected to the first input of the second switch and the second output of the first switch is connected to the second input of the second switch. In one or more embodiments, the switches each comprise a wafer (e.g., semiconductor such as silicon wafer) having a low doping (ideally none) to minimize absorption in off-state, see.

[0098] Block 1102 represents inputting electromagnetic radiation to a first one of the switches. Block 1104 represents activating the switches to perform swap of electromagnetic radiation (inputted at the first input or the second input or both the first input and the second input) between the two pathways so as to redirect: (i) , a first portion of the electromagnetic radiation from the first pathway to the second pathway and; (ii) a second portion of the electromagnetic radiation from the second pathway to the first pathway; and activating the second switch later than first switch so that a combination of the swap in the first switch and the swap in the second switch outputs a pulse at the second output of the second switch and a complementary pattern of the electromagnetic radiation at the first output of the second switch when the electromagnetic radiation is inputted to the first input of first switch. Fig.12 illustrates an example device 1200 which can be used to implement the method. As illustrated in Fig.12, the device comprises a first path 1202 for guiding electromagnetic radiation; a second path 1204 for guiding the electromagnetic radiation; and a plurality of switches 1206 positioned in series along the paths. Each of the switches have a first input 1208 and a second input 1210; a first output 1212 and a second output 1214; wherein the first input is coupled to the first output and the second input is coupled to the second output when the switch is not activated; and a control input 1216 for receiving control signals for activating the switch so as to perform a swap of electromagnetic radiation (inputted at either the first input or the second input) between the two paths. For each pair of adjacent ones of the switches comprising a first switch and a second switch, the first output of the first switch is connected to the first input of the second switch, and the second output of the first switch is connected to the second input of the second switches. As described herein, the activating redirects (i) electromagnetic radiation from the first path to the second path; and (ii) electromagnetic radiation from the second path to the first path. Hardware Environment FIG.13 is an exemplary hardware and software environment 1300 (referred to as a computer-implemented system and / or computer-implemented method) used to implement one or more embodiments of the invention (pulse synthesizer 1330). The hardware and software environment includes a computer 1302 and may include peripherals. Computer 1302 may be a user / client computer, server computer, or may be a database computer. The computer 1302 comprises a hardware processor 1304A and / or a special purpose hardware processor 1304B (hereinafter alternatively collectively referred to as processor 1304) and a memory 1306, such as random access memory (RAM). The computer 1302 may be coupled to, and / or integrated with, other devices, including input / output (I / O) devices such as a keyboard 1314, a cursor control device 1316 (e.g., a mouse, a pointing device, pen and tablet, touch screen, multi-touch device, etc.) and a printer 1328. In one or more embodiments, computer 1302 may be coupled to, or may comprise, a portable or media viewing / listening device 1332 (e.g., an MP3 player, IPOD, NOOK, portable digital video player, cellular device, personal digital assistant, etc.). In yet another embodiment, the computer 1302 may comprise a multi-touch device, mobile phone, gaming system, internet enabled television, television set top box, or other internet enabled device executing on various platforms and operating systems. In one embodiment, the computer 1302 operates by the hardware processor 1304A performing instructions defined by the computer program 1310 (e.g., a switch activating application) under control of an operating system 1308. The computer program 1310 and / or the operating system 1308 may be stored in the memory 1306 and may interface with the user and / or other devices to accept input and commands and, based on such input and commands and the instructions defined by the computer program 1310 and operating system 1308, to provide output and results. Output / results may be presented on the display 1322 or provided to another device for presentation or further processing or action. In one embodiment, the display 1322 comprises a liquid crystal display (LCD) having a plurality of separately addressable liquid crystals. Alternatively, the display 1322 may comprise a light emitting diode (LED) display having clusters of red, green and blue diodes driven together to form full-color pixels. Each liquid crystal or pixel of the display 1322 changes to an opaque or translucent state to form a part of the image on the display in response to the data or information generated by the processor 1304 from the application of the instructions of the computer program 1310 and / or operating system 1308 to the input and commands. The image may be provided through a graphical user interface (GUI) module 1318. Although the GUI module 1318 is depicted as a separate module, the instructions performing the GUI functions can be resident or distributed in the operating system 1308, the computer program 1310, or implemented with special purpose memory and processors. In one or more embodiments, the display 1322 is integrated with / into the computer 1302 and comprises a multi-touch device having a touch sensing surface (e.g., track pod or touch screen) with the ability to recognize the presence of two or more points of contact with the surface. Examples of multi-touch devices include mobile devices (e.g., IPHONE, NEXUS S, DROID devices, etc.), tablet computers (e.g., IPAD, HP TOUCHPAD, SURFACE Devices, etc.), portable / handheld game / music / video player / console devices (e.g., IPOD TOUCH, MP3 players, NINTENDO SWITCH, PLAYSTATION PORTABLE, etc.), touch tables, and walls (e.g., where an image is projected through acrylic and / or glass, and the image is then backlit with LEDs). Some or all of the operations performed by the computer 1302 according to the computer program 1310 instructions may be implemented in a special purpose processor 1304B. In this embodiment, some or all of the computer program 1310 instructions may be implemented via firmware instructions stored in a read only memory (ROM), a programmable read only memory (PROM) or flash memory within the special purpose processor 1304B or in memory 1306. The special purpose processor 1304B may also be hardwired through circuit design to perform some or all of the operations to implement the present invention. Further, the special purpose processor 1304B may be a hybrid processor, which includes dedicated circuitry for performing a subset of functions, and other circuits for performing more general functions such as responding to computer program 1310 instructions. In one embodiment, the special purpose processor 1304B is an application specific integrated circuit (ASIC) or field programmable gate array. The computer 1302 may also implement a compiler 1312 that allows an application or computer program 1310 written in a programming language such as C, C++, Assembly, SQL, PYTHON, PROLOG, MATLAB, RUBY, RAILS, HASKELL, or other language to be translated into processor 1304 readable code. Alternatively, the compiler 1312 may be an interpreter that executes instructions / source code directly, translates source code into an intermediate representation that is executed, or that executes stored precompiled code. Such source code may be written in a variety of programming languages such as JAVA, JAVASCRIPT, PERL, BASIC, etc. After completion, the application or computer program 1310 accesses and manipulates data accepted from I / O devices and stored in the memory 1306 of the computer 1302 using the relationships and logic that were generated using the compiler 1312. The computer 1302 also optionally comprises an external communication device such as a modem, satellite link, Ethernet card, or other device for accepting input from, and providing output to, other computers 1302. In one embodiment, instructions implementing the operating system 1308, the computer program 1310, and the compiler 1312 are tangibly embodied in a non-transitory computer-readable medium, e.g., data storage device 1320, which could include one or more fixed or removable data storage devices, such as a zip drive, floppy disc drive 1324, hard drive, CD-ROM drive, tape drive, etc. Further, the operating system 1308 and the computer program 1310 are comprised of computer program 1310 instructions which, when accessed, read and executed by the computer 1302, cause the computer 1302 to perform the steps necessary to implement and / or use the present invention or to load the program of instructions into a memory 1306, thus creating a special purpose data structure causing the computer 1302 to operate as a specially programmed computer executing the method steps described herein. Computer program 1310 and / or operating instructions may also be tangibly embodied in memory 1306 and / or data pulse synthesizer 1330, thereby making a computer program product or article of manufacture according to the invention. As such, the terms “article of manufacture,” “program storage device,” and “computer program product,” as used herein, are intended to encompass a computer program accessible from any computer readable device or media. Of course, those skilled in the art will recognize that any combination of the above components, or any number of different components, peripherals, and other devices, may be used with the computer 1302. FIG.14 schematically illustrates a typical distributed / cloud-based computer system 1400 using a network 1404 to connect client computers 1402 to server computers 1406. A typical combination of resources may include a network 1404 comprising the Internet, LANs (local area networks), WANs (wide area networks), SNA (systems network architecture) networks, or the like, clients 1402 that are personal computers or workstations (as set forth in FIG.13), and servers 1406 that are personal computers, workstations, minicomputers, or mainframes (as set forth in FIG.13). However, it may be noted that different networks such as a cellular network (e.g., GSM [global system for mobile communications] or otherwise), a satellite based network, or any other type of network may be used to connect clients 1402 and servers 1406 in accordance with embodiments of the invention. A network 1404 such as the Internet connects clients 1402 to server computers 1406. Network 1404 may utilize ethernet, coaxial cable, wireless communications, radio frequency (RF), etc. to connect and provide the communication between clients 1402 and servers 1406. Further, in a cloud-based computing system, resources (e.g., storage, processors, applications, memory, infrastructure, etc.) in clients 1402 and server computers 1406 may be shared by clients 1402, server computers 1406, and users across one or more networks. Resources may be shared by multiple users and can be dynamically reallocated per demand. In this regard, cloud computing may be referred to as a model for enabling access to a shared pool of configurable computing resources. Clients 1402 may execute a client application or web browser and communicate with server computers 1406 executing web servers 1410. Such a web browser is typically a program such as MICROSOFT INTERNET EXPLORER / EDGE, MOZILLA FIREFOX, OPERA, APPLE SAFARI, GOOGLE CHROME, etc. Further, the software executing on clients 1402 may be downloaded from server computer 1406 to client computers 1402 and installed as a plug-in or ACTIVEX control of a web browser. Accordingly, clients 1402 may utilize ACTIVEX components / component object model (COM) or distributed COM (DCOM) components to provide a user interface on a display of client 1402. The web server 1410 is typically a program such as MICROSOFT’S INTERNET INFORMATION SERVER. Web server 1410 may host an Active Server Page (ASP) or Internet Server Application Programming Interface (ISAPI) application 1412, which may be executing scripts. The scripts invoke objects that execute business logic (referred to as business objects). The business objects then manipulate data in database 1416 through a database management system (DBMS) 1414. Alternatively, database 1416 may be part of, or connected directly to, client 1402 instead of communicating / obtaining the information from database 1416 across network 1404. When a developer encapsulates the business functionality into objects, the system may be referred to as a component object model (COM) system. Accordingly, the scripts executing on web server 1410 (and / or application 1412) invoke COM objects that implement the business logic. Further, server 1406 may utilize MICROSOFT’S TRANSACTION SERVER (MTS) to access required data stored in database 1416 via an interface such as ADO (Active Data Objects), OLE DB (Object Linking and Embedding DataBase), or ODBC (Open DataBase Connectivity). Generally, these components 1400-1416 all comprise logic and / or data that is embodied in / or retrievable from device, medium, signal, or carrier, e.g., a data storage device, a data communications device, a remote computer or device coupled to the computer via a network or via another data communications device, etc. Moreover, this logic and / or data, when read, executed, and / or interpreted, results in the steps necessary to implement and / or use the present invention being performed. Although the terms “user computer”, “client computer”, and / or “server computer” are referred to herein, it is understood that such computers 1402 and 1406 may be interchangeable and may further include thin client devices with limited or full processing capabilities, portable devices such as cell phones, notebook computers, pocket computers, multi-touch devices, and / or any other devices with suitable processing, communication, and input / output capability. Of course, those skilled in the art will recognize that any combination of the above components, or any number of different components, peripherals, and other devices, may be used with computers 1402 and 1406. Embodiments of the invention are implemented as a software / pulse synthesis or switching application on a client 1402 or server computer 1406. Further, as described above, the client 1402 or server computer 1406 may comprise a thin client device or a portable device that has a multi-touch-based display. Device Embodiments Illustrative embodiments include, but are not limited to, the following (referring also to Figs.1-14. 1. Fig.1 and Fig.2 illustrate an example of a slicer module 100, comprising: a switch 101 comprising a medium 102 comprising a property that can be modulated to switch the medium between a transmissive state and a reflective state; control inputs 104a, 104b for receiving control signals for modulating the property to switch between the transmissive state and the reflective state at a region 106 of the medium; a first input 108 and a second input 110; a first output 112 and a second output 114; a first path 116 defined as coupling the first input to the first output when the switch is not activated; a second path 118 defined as coupling the second input to the second output when the switch is not activated; and wherein: the first path and the second path intersect at the region 106 of the medium so that activation of the switch by the control signals performs a swap of electromagnetic radiation (inputted at either the first input or the second input) between the two paths, redirecting: (i) electromagnetic radiation 120 from the first path to the second path; and (ii) electromagnetic radiation from the second path to the first path . 2. A pair 202, 204 of the slicer modules of embodiment 1, wherein: the first output of the first module is connected to the first input of the second module; the second output of the first module 202 is connected to the second input of the second module 204; the switch in the second module is activated later than the switch in the first module so that a combination of the swap in the first module and the swap in the second module outputs a pulse 126 at the second output the second module and a complementary pattern 128 of the electromagnetic radiation at the first output of the second module when the electromagnetic radiation is inputted to the first input of the first module. 3. A plurality m of the pairs of embodiment 2, wherein: m is an integer, the switch in the next module 204 is activated later than the switch in the immediately preceding one 202 of the modules, resulting in sequences of the pulses 124, the duration of the one of the pulses outputted from the mthone of the pairs is determined by the time separation between activation of the two switches in the mthone of the pairs, and the time separation between the end of the pulse outputted from the (m-1)thpair and the beginning of the pulse outputted from the first module of the mthpair is determined by the time separation between activation of the switch in the second module of the (m-1)thpair and the switch in first module of the mthone of the pairs. 4. The slicer module of any of the embodiments 1-3, further comprising: a controller 210 controlling application of the control signals to control timing of the transmissive state and the reflective state for the electromagnetic radiation inputted onto the medium. 5. The slicer of any of the embodiments 1-4, further comprising a laser system (laser 1, laser 2) coupling the control signals comprising: a laser beam input 212 onto the medium 102 to modulate the property in the region of the medium on which the electromagnetic radiation is incident. 6. The slicer of embodiment 5, wherein the laser beams are tuned to optical transitions to excite charge carriers that interact with the electromagnetic radiation to cause reflection of the electromagnetic radiation in the reflective state. 7. The slicer of any of the embodiments 1-5, wherein the paths each comprise an arrangement or system of mirrors 122 for directing the electromagnetic radiation in a folded configuration. 8. The slicer of any of the embodiments 1-7, wherein the medium comprises a semiconductor with a specular surface for reflecting the electromagnetic radiation in the reflective state. 9. The slicer of any of the embodiments 1-8, further comprising mirrors 122 directing the electromagnetic radiation onto the medium at Brewster’s angle to maximize a contrast between the transmissive state and the reflective state. 10. The slicer of any of the embodiments 1-9, wherein the medium comprises a silicon wafer and the electromagnetic radiation comprises terahertz radiation having a frequency between 0.1-100 THz. 11. The slicer of any of the embodiments 1-10, wherein the pulses each have a duration of at least 1 ns or in a range of 1ns – 1 millisecond (1 nanosecond – 1 millisecond). 12. The slicer of any of the embodiments 1-10, wherein the pulses each have a duration of at least 100 femtoseconds (fs) or in a range of 100 fs – 1 millisecond. 13. The slicer of any of the embodiments 1-12, wherein the paths are folded and directed in a vertical and horizontal dimension to form a compact module. 14. A module of any of the embodiments 1-13 configured in a pair of modules, wherein each pair has a volume V smaller than 250 mm by 250 mm by 500 mm or a volume smaller than 500 mm by 500 mm by 1000mm. 15. The slicer of any of the embodiments 1-14, wherein the property of the media is modulated using the control signals comprising electrical signals. 16. A pulse slicing system comprising an assembly of modules of any of the embodiments 1-15, wherein: the switching is characterized by high on / off contrast (e.g., 60-70 dB), low insertion loss (e.g.1.2 dB) and can be controlled for customizable pulse length; and the pulses have the same spatial mode properties as the input electromagnetic radiation but can have their phase independently controlled. 17. A pulse slicing system comprising an assembly of modules of any of the embodiments 1-16, wherein the switching is controlled so that the pulses in the additive channel comprise a desired pulse sequence. 18. The slicer of any of the embodiments 1-17, further comprising a motorized mechanism 402 for rotatably inserting and removing the medium from the slicer module along a rotation path and controlling positioning of the medium at the intersection between the paths. In one or more embodiments, the mechanism is configured or operable to maintain (e.g., the mechanism optionally further comprises a combination or assembly of set screws 404 and springs maintaining) alignment of the medium with the intersection for multiple insertions and removals of the medium along the path of the rotation R and for a given range of frequencies of the electromagnetic radiation. 19. The slicer of embodiment 1-18, wherein the medium comprises a wafer having a thickness tailored for minimizing unwanted reflections of the electromagnetic radiation. 20. The slicer module of any of the embodiments 1-19 configured for outputting the pulses using a gyrotron as the input. 21. The slicer module of any of the embodiments 1-20 configured for outputting pulses for use in a magnetic resonance experiment. 22. The method or device of any of the embodiments 1-21, wherein the complementary pattern 128 comprises a time envelope or profile equal to a time envelope or profile of the electromagnetic radiation 130 inputted at the first input minus the time envelope of the pulse 126 at the second output. 23. The switch of any of the embodiments, wherein the switch (e.g., silicon wafer) has at least 70% (e.g., at least 90%) reflection in the on state. 24. A device comprising or useful in a pulse synthesizer or generator or arbitrary waveform generator, comprising: a first path for guiding electromagnetic radiation; a second path for guiding the electromagnetic radiation; a plurality of switches positioned in series along the paths; each of the switches having: a first input and a second input; a first output and a second output; wherein the first input is coupled to the first output and the second input is coupled to the second output when the switch is not activated; a control input for receiving a control signal for activating the switch so as to perform a swap of electromagnetic radiation (inputted at at least one of the first input or the second input) between the two paths, redirecting: (i) electromagnetic radiation from the first path to the second path; and (ii) electromagnetic radiation from the second path to the first path; and for each pair of adjacent ones of the switches comprising a first switch and a second switch, the first output of the first switch is connected to the first input of the second switch, and the second output of the first switch is connected to the second input of the second switch. 25.The device of embodiment 24, further comprising a computer 1300 or circuit (e.g., application specific integrated circuit or field programmable gate array) executing, or a non-transitory machine readable medium including instructions which, when executed by the circuit or one or more processors in the computer, cause the one or more processors or the circuit to perform operations comprising activating, using the control signals inputted at the control inputs, the second switch later than the first switch so that a combination of the swap in the first switch and the swap in the second switch outputs a pulse at the second output of the second switch and a complementary pattern of the electromagnetic radiation at the first output of the second switch when the electromagnetic radiation is inputted to the first input of the first switch. 26. The device of embodiment 24or 25 , further comprising a plurality m of the pairs of the first switch and the second switch wherein the operations further comprise:: activating the next one of the switches later than the immediately preceding one of the switches with: (i) a time separation between the activating of the two switches in the mthone of the pairs to set a duration of the one of the pulses outputted from the mthone of the pairs; and (ii) a time separation between the activating of the second switch of the (m-1)thpair and the first switch of the mthone of the pairs to set the time separation between the end of the pulse outputted from the (m-1)thpair and the beginning of the pulse outputted from the first switch of the mthpair. 25. 26. The device of any of the embodiments 24-25 implemented as or comprising a photonic integrated circuit comprising the switches and paths. 27. 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[0098] https: / / www.spiedigitallibrary.org / conference-proceedings-of- spie / 2842 / 0000 / Generation-of-picosecond-far-infrared-pulses-using-laser- activated-semiconductor / 10.1117 / 12.262736.full. Conclusion This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A device useful in a pulse synthesizer or generator, comprising: a first path for guiding electromagnetic radiation; a second path for guiding the electromagnetic radiation; a plurality of switches positioned in series along the paths; each of the switches having: a first input and a second input; a first output and a second output; wherein the first input is coupled to the first output and the second input is coupled to the second output when the switch is not activated; a control input for receiving a control signal for activating the switch so as to perform a swap of electromagnetic radiation (inputted at at least one of the first input or the second input) between the two paths, redirecting: (iii) electromagnetic radiation from the first path to the second path; and (iv) electromagnetic radiation from the second path to the first path; and for each pair of adjacent ones of the switches comprising a first switch and a second switch, the first output of the first switch is connected to the first input of the second switch, and the second output of the first switch is connected to the second input of the second switch.

2. The device of claim 1, further comprising a computer or circuit executing, or a non-transitory machine readable medium including instructions which, when executed by the circuit or one or more processors in the computer, cause the one or more processors or the circuit to perform operations comprising activating, using the control signals inputted at the control inputs, the second switch later than the first switch so that a combination of the swap in the first switch and the swap in the second switch outputs a pulse at the second output of the second switch and a complementary pattern of the electromagnetic radiation at the first output of the second switch when the electromagnetic radiation is inputted to the first input of the first switch.

3. The device of claim 2, further comprising a plurality m of the pairs of the first switch and the second switch wherein the operations further comprise:: activating the next one of the switches later than the immediately preceding one of the switches with:(iii) a time separation between the activating of the two switches in the mthone of the pairs to set a duration of the one of the pulses outputted from the mthone of the pairs; and (iv) a time separation between the activating of the second switch of the (m-1)thpair and the first switch of the mthone of the pairs to set the time separation between the end of the pulse outputted from the (m-1)thpair and the beginning of the pulse outputted from the first switch of the mthpair.

4. A slicer module, comprising: a switch comprising a medium comprising a property that can be modulated to switch the medium between a transmissive state and a reflective state; control inputs for receiving control signals for modulating the property to switch between the transmissive state and the reflective state at a region of the medium; a first input and a second input; a first output and a second output; a first path defined as coupling the first input to the first output when the switch is not activated; a second path defined as coupling the second input to the second output when the switch is not activated; and wherein: the first path and the second path intersect at the region of the medium so that activation of the switch by the control signals performs a swap of electromagnetic radiation (inputted at at least one of the first input or the second input) between the two paths, redirecting: (iii) electromagnetic radiation from the first path to the second path; and (iv) electromagnetic radiation from the second path to the first path .

5. A pair of the slicer modules of claim 4, wherein: the first output of the first module is connected to the first input of the second module; the second output of the first module is connected to the second input of the second module; the switch in the second module is activated later than the switch in the first module so that a combination of the swap in the first module and the swap in the second module outputs a pulse at the second output of the second module and a complementary pattern of theelectromagnetic radiation at the first output of the second module when the electromagnetic radiation is inputted to the first input of the first module.

6. A plurality m of the pairs of the modules in claim 5, wherein: m is an integer, the switch in the next module is activated later than the switch in the immediately preceding one of the modules, resulting in sequences of the pulses, the duration of the one of the pulses outputted from the mthone of the pairs is determined by the time separation between the activation of the two switches in the mthone of the pairs, and the time separation between the end of the pulse outputted from the (m-1)thpair and the beginning of the pulse outputted from the first module of the mthpair is determined by the time separation between the activation of the switch in the second module of the (m-1)thpair and the switch in first module of the mthone of the pairs.

7. The slicer module of claim 4, further comprising: a controller controlling application of the control signals to control timing of the transmissive state and the reflective state for the electromagnetic radiation inputted onto the medium.

8. The slicer of claim 4, further comprising a laser system coupling the control signals comprising: a laser beam input onto the medium to modulate the property in the region of the medium on which the electromagnetic radiation is incident.

9. The slicer of claim 8, wherein the laser beams are tuned to optical transitions to excite charge carriers that interact with the electromagnetic radiation to cause reflection of the electromagnetic radiation in the reflective state.

10. The slicer of claim 5, wherein the paths each comprise an arrangement or system of mirrors for directing the electromagnetic radiation in a folded configuration.

11. The slicer of claim 4, wherein the medium comprises a semiconductor with a specular surface for reflecting the electromagnetic radiation in the reflective state.

12. The slicer of claim 4, further comprising mirrors directing the electromagnetic radiation onto the medium at Brewster’s angle to maximize a contrast between the transmissive state and the reflective state.

13. The slicer of claim 4, wherein the medium comprises a silicon wafer and the electromagnetic radiation comprises terahertz radiation having a frequency between 0.1-100 THz.

14. The slicer of claim 5 or 6, wherein the pulses each have a duration of at least 1 ns or in a range of 1ns – 1 millisecond.

15. The slicer of claim 5 or 6, wherein the pulses each have a duration of at least 100 fs or in a range of 100 fs – 1 millisecond.

16. The slicer of claim 5 or 6, wherein the paths are folded and directed in a vertical and horizontal dimension to form a compact module.

17. The slicer of claim 5, wherein each pair has a volume smaller than 250 mm by 250 mm by 500 mm or a volume smaller than 500 mm by 500 mm by 1000mm.

18. The slicer of claim 4, wherein the property of the medium is modulated using the control signals comprising electrical signals.

19. A pulse slicing system comprising an assembly of modules of claim 5 wherein: the switching is characterized by high on / off contrast, low insertion loss and can be controlled for customizable pulse length; and the pulses have the same spatial mode properties as the input electromagnetic radiation but can have their phase independently controlled.

20. A pulse slicing system comprising an assembly of modules of claim 5, wherein the switching is controlled so that the pulses in the path comprising an additive channel comprise a desired pulse sequence.

21. The slicer of claim 6, further comprising a motorized mechanism operable to rotatably insert and remove the medium from the slicer module along a rotation path and controlling positioning of the medium at the intersection between the paths, the mechanism further comprising a combination of set screws and springs maintaining alignment of the medium with the intersection for multiple insertions and removals of the medium along the path of the rotation and for a given range of frequencies of the electromagnetic radiation.

22. The slicer of claim 4, wherein the medium comprises a wafer having a thickness tailored for minimizing unwanted reflections of the electromagnetic radiation.

23. A system comprising the slicer module of claim 4 configured for outputting the pulses using a gyrotron as the source of the electromagnetic radiation inputted to the module.

24. The slicer module of claim 4 configured for outputting pulses configured for use in a magnetic resonance, spectroscopy, electron spin resonance, or communication of information .

25. A method of synthesizing pulses, comprising: using one or more pairs of switches comprising a first switch and a second switch coupling a first pathway and a second pathway, each of the switches comprising a first input; a second input; a first output; a second output; a first output and a second output; wherein the first input is coupled to the first output and the second input is coupled to the second output when the switch is not activated; and wherein: the first output of the first switch is connected to the first input of the second switch and the second output of the first switch is connected to the second input of the second switch; and the method further comprising: activating the switches to perform swap of electromagnetic radiation (inputted at at least one of the first input or the second input) between the two pathways so as to redirect:(v) , a first portion of the electromagnetic radiation from the first pathway to the second pathway and; (vi) a second portion of the electromagnetic radiation from the second pathway to the first pathway; and activating the second switch later than first switch so that a combination of the swap in the first switch and the swap in the second switch outputs a pulse at the second output of the second switch and a complementary pattern of the electromagnetic radiation at the first output of the second switch when the electromagnetic radiation is inputted to the first input of first switch.

26. The method of claim 25, comprising a plurality m of the pairs of the modules, wherein m is an integer, the method further comprising generating a sequence of pulses by: activating the next one of the switches later than the immediately preceding one of the switches: controlling the time separation between the activation of the two switches in the mthone of the pairs to set a duration of the one of the pulses outputted from the mthone of the pairs; and controlling the time separation between the second switch of the (m-1)thpair and the first switch of the mthone of the pairs so as to set the time separation between the end of the pulse outputted from the (m-1)thpair and the beginning of the pulse outputted from the first switch of the mthpair.

27. The device of claims 2 or 5, wherein the complementary pattern comprises a time envelope or profile equal to a time envelope or profile of the electromagnetic radiation inputted at the first input minus the time envelope of the pulse at the second output.

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