Valley Current Generation Using Superimposed Polarized Light Pulses
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Solution Overview
Problem
Existing methods for generating valley currents in solid materials, particularly in two-dimensional Dirac materials like graphene, are limited by the need for complex radiation fields and lack practical controllability, making them unsuitable for practical applications in valleytronics.
Innovation Solution
A method and apparatus using pulsed radiation with superimposed radiation pulses of different frequencies and polarizations, specifically ultraviolet, visible, and infrared light, to create a net electrical charge carrier current by selectively exciting valley states in the material, without external potential or mechanical strain, allowing for precise control of valley currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex radiation fields are used to generate valley currents, then valley current generation is achieved, but device complexity and ease of operation deteriorate
Solution Approach 1:
The complex radiation field is segmented into multiple simple pulsed radiation fields with different center frequencies (first, second, third frequencies). Each pulse individually interacts with the material, and their superposition creates the desired valley current effect without requiring a single complex radiation field. This divides the complex task into manageable sequential steps.
Solution Approach 2:
Multiple simple pulsed radiation fields with different frequencies are merged through superposition to achieve the valley current generation effect. The patent combines these pulses in time and space, creating an effective complex radiation field from simpler components that can be individually controlled and generated.
2Reliability
If complex radiation fields are used to generate valley currents, then valley current generation is achieved, but ease of operation worsens
Solution Approach 1:
The operation is segmented into controlling multiple independent pulsed radiation fields with simple characteristics (different frequencies, polarizations, and timings) rather than controlling a single complex radiation field. Each pulse can be independently generated and adjusted, making the overall system easier to operate and control.
Solution Approach 2:
The patent changes multiple parameters of the radiation field (center frequencies, polarization states, pulse timings, and intensities) to achieve valley current generation. By adjusting these individual parameters of simple pulses, the system becomes more controllable and operable compared to manipulating a single complex radiation field.
3Ease of operation
If external potential or mechanical strain is applied, then valley current control is achieved, but device complexity and loss of energy increase
Solution Approach 1:
The patent replaces mechanical strain methods with optical field methods for controlling valley currents. Instead of applying physical stress or mechanical deformation to the material, the invention uses tailored pulsed radiation fields with specific frequencies and polarizations to directly manipulate the electronic states and generate valley currents, eliminating the need for mechanical components and associated energy losses.
Solution Approach 2:
The patent replaces external potential application with optical field manipulation. Rather than using electrical fields or voltage gradients to control carrier movement, the invention employs carefully designed optical pulses that directly couple to the material's electronic transitions and generate valley-selective currents through optical selection rules, reducing energy loss compared to electrical control methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables practical generation and control of valley currents with high controllability and selectivity, facilitating applications in optical signal processing, data storage, and logical operations, and providing insights into sub-optical-cycle dynamics.
Implementation Method 1
irradiating the solid material with pulsed radiation comprising polarized radiation pulses, which are created by a superposition of first radiation pulses having a first centre frequency and a first electric field with a first electric field polarization and second radiation pulses having a second centre frequency and a second electric field with a second electric field polarization
Implementation Method 2
polarized radiation pulses, which are created by a superposition of first radiation pulses having a first centre frequency and a first electric field with a first electric field polarization and second radiation pulses having a second centre frequency
Data Source
Figure 1~2
Figure 3A~3C
Figure 4~5B
AI summary
A valley current generating method for manipulating charge carriers in a solid material 10, having a band structure with a Brillouin zone including valleys localized in the Brillouin zone, comprises a step of irradiating the solid material 10 with pulsed radiation comprising polarized radiation pulses 3, which are created by a superposition of first radiation pulses 1 having a first centre frequency and a first electric field with a first electric field polarization and second radiation pulses 2 having a second centre frequency and a second electric field with a second electric field polarization, wherein the first and second centre frequencies differ from each other, the polarized radiation pulses 3 have an electric field shaped such that a net electrical charge carrier current is created in the solid material 10 by one of the valleys, each of the first and second centre frequencies is included in a spectral range covering at least one of ultraviolet, visible and infrared light frequencies, and the electric field of the polarized radiation pulses 3 is shaped by setting the first and second electric field polarizations such that they differ from each other and by setting a relative phase of the first and second electric fields. Furthermore, a valley current generating apparatus 100 for manipulating charge carriers in a solid material 10 and methods of using the valley current generating method or apparatus are disclosed.