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Next-generation 6G communication holds the potential to revolutionize data transfer, enabling the realization of eXtended Reality (XR) with enhanced sensory experiences. To achieve this, advanced components such as high-performance intensity/phase modulators, waveguides, multiplexers, splitters, combiners, and filters operating in terahertz (THz) regime, specifically within the frequency range of 0.1–1 THz, are essential. However, existing microwave equipment and vector network analyzers designed for this frequency range suffer from limitations in resolution, stability, and accuracy when evaluating the intensity and phase responses of critical 6G THz devices. In this comprehensive review, we delve into the critical device requirements and emerging trends in next-generation 6G communication, essential performance evaluation parameters, comparisons between microwave and nano/microphotonic devices for testing, and the application of high-resolution THz sensors in 6G Internet-of-Things (IoT) scenarios. Notably, a frequency comb in the photonic regime emerges as the prime candidate for achieving precision evaluations of 6G networks and devices. Consequently, this review highlights the latest research in frequency comb measurements in the 6G THz frequency regime, with a particular emphasis on nano/microphotonic devices and metamaterials. The integration of frequency comb measurements into 6G and THz photonic devices and networks promises to accelerate the realization of high-density next-generation 6G communication.

Laser ablation of metal thin films draws attention as a fast means of clean micropatterning. In this study, we attempt to remove only the metal thin film layer selectively without leaving thermal damage on the underneath substrate. Specifically, our single-pulse ablation experiment followed by two-temperature analysis explains that selective ablation can be achieved for gold (Au) films of 50–100 nm thickness by the lift-off process induced as a result of vaporization of the titanium (Ti) interlayer with a strong electron–phonon coupling. With increasing the film thickness comparable to the mean free path of electrons (100 nm), the pulse duration has to be taken shorter than 10 ps, as high-temperature electrons generated by the ultrashort pulses transfer heat to the Ti interlayer. We verify the lift-off ablation by implementing millimeters-scale micropatterning of optoelectronic devices without degradation of optical properties.

The realization of hybrid optics could be one of the best ways to fulfill the technological requirements of compact, light-weight, and multi-functional optical systems for modern industries. Planar diffractive lens (PDL) such as diffractive lenses, photonsieves, and metasurfaces can be patterned on ultra-thin flexible and stretchable substrates and be conformally attached on top of arbitrarily shaped surfaces. In this review, we introduce recent research works addressed to the design and manufacturing of ultra-thin graphene optics, which will open new markets in compact and light-weight optics for next-generation endoscopic brain imaging, space internet, real-time surface profilometry, and multi-functional mobile phones. To provide higher design flexibility, lower process complexity, and chemical-free process with reasonable investment cost, direct laser writing (DLW) of laser-induced-graphene (LIG) is actively being applied to the patterning of PDL. For realizing the best optical performances in DLW, photon-material interactions have been studied in detail with respect to different laser parameters; the resulting optical characteristics have been evaluated in terms of amplitude and phase. A series of exemplary laser-written 1D and 2D PDL structures have been actively demonstrated with different base materials, and then, the cases are being expanded to plasmonic and holographic structures. The combination of these ultra-thin and light-weight PDL with conventional bulk refractive or reflective optical elements could bring together the advantages of each optical element. By integrating these suggestions, we suggest a way to realize the hybrid PDL to be used in the future micro-electronics surface inspection, biomedical, outer space, and extended reality (XR) industries. We present how direct-laser-writing can be utilized to fabricate ultra-thin light-weight planar diffractive optics with graphene as the base material. (Inset scale bar: 1 mm).

Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron–phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.

In the pursuit of carbon neutrality policies, the development of eco‐friendly and intelligent furniture commands a significant role. However, the integration of non‐biodegradable electronic components in smart furniture fabrication has led to substantial electronic waste. Here, we report a straightforward approach, the rapid production of Laser‐Induced Graphene (LIG) on medium‐density fiberboard (MDF), a prevalent recycled wood in furniture production. This LIG electrode is crafted with negligible material ablation in ambient air with the aid of femtosecond laser pulses, without requiring any additional materials, showcasing the highest electrical conductivity (2.781 Ω sq−1) among previously reported lignocellulosic materials‐based LIG. The application of this LIG electrode for lighting, heating, and touch sensors displays sufficient performance for smart furniture implementation. For eco‐conscious furniture, LIG‐based human‐machine interfaces are demonstrated on recycled woods for the facile control of smart devices, which will readily enable IoT‐oriented smart sustainable furniture. We demonstrate the direct patterning of femtosecond Laser‐Induced Graphene (LIG) onto recycled wood, creating key electrical components for green smart furniture. These LIG electrodes set a record‐breaking electrical conductivity record at 2.781 Ω sq−1 among lignocellulosic LIGs. Our LIG‐based capacitive touch sensor controls the light brightness, adjusts the stove warmer temperature, and operates the computer interface.

The ascent of internet of things (IoT) technology has increased the demand for glass electronics. However, the production of glass electronics necessitates complicated processes, including conductive materials coating and chemical vapor deposition, which entail the use of additional chemicals. Consequently, this raises environmental apprehensions concerning chemical and electronic waste. In this study, a fast, cost‐effective, and simple approach are presented to meet the growing demand for glass electronics while addressing environmental concerns associated with their production processes. The method involves converting polyimide (PI) tape into laser‐induced graphene (LIG) and transferring it onto a glass substrate using ultraviolet laser direct writing technology. This process allows for the fabrication of LIG‐embedded glass without additional chemical treatments in ambient air. Subsequently, the residual PI tape is removed, resulting in LIG‐based glass electrodes with an electrical resistivity of 1.065 × 10−3 Ω m. These LIG electrodes demonstrate efficient functionality for window applications such as defogging, heating, temperature sensing, and solar warming, suitable for automotive and residential windows. The potential scalability of this eco‐friendly technology to IoT‐based smart and sustainable window electronics further underscores its adaptability to meet diverse user needs. Herein, the UV laser direct writing and in situ transfer of laser‐induced graphene (LIG) are demonstrated on glass to form key electrical components for smart windows applications. These LIG electrodes demonstrate efficient functionality for window applications such as defogging, heating, temperature sensing, and solar warming, suitable for automotive and residential windows.

Aging society is a global challenge, with increasing healthcare demands and associated social costs. Monitoring body temperature is crucial for early diagnosis and effective treatment of medical conditions, particularly in the elderly. Herein, a smart denture with embedded thin‐film temperature sensors designed to monitor the body temperature in real‐time is presented, which can be commonly worn by the elderly population for advanced healthcare. This device is realized using polymethyl methacrylate resin plates and dentures, which are routinely employed materials in dentistry for prosthesis fabrication. The thin‐film temperature sensor is patterned using femtosecond laser pulses, ensuring high mechanical strength, high lateral resolution, and high‐temperature sensitivity (0.26% °C−1). Furthermore, experiments conducted in a virtual intraoral wet environment demonstrate the sensor's capability to accurately measure the small temperature variation of 0.1 °C within a short timeframe. The integration of temperature sensors into dentures holds promise for enhancing patient monitoring and improving overall healthcare outcomes for the elderly population. The versatility of direct laser writing concept with femtosecond lasers will enable the implementation of various sensors, energy storage devices, and circuitries into dentures for advanced smart healthcare. We demonstrate the direct‐laser patterning of a gold thin film on polymethyl methacrylate  to fabricate a temperature sensor for dentures. The temperature sensor‐embedded smart dentures are evaluated in an oral environment, enabling in‐situ monitoring for elderly healthcare. The sensor effectively track activities such as drinking hot or cold water and speaking.

Evolving demands for compact, light-weight, and versatile optical systems across various industries require the facile integration of planar diffractive optics. For the manufacturing of diffractive optics, green manufacturing becomes the prerequisite with timely considerations of Environmental, Social, and Governance (ESG). Conventional manufacturing processes such as semiconductor lithography or nano /micro imprinting utilize a large amount of harmful chemicals. Meanwhile, direct laser writing emerges as one of the key solution candidates, offering clear advantages over others, especially in terms of eco-friendliness due to the simple manufacturing process with less chemical usage. In this comprehensive review, we present recent advances in the analytical design, green manufacturing of electrically tunable smart light-weight planar optics, and their promising applications in space optics, photovoltaics, and optical imaging, highlighting the necessity for tunability in focal length, aberration, transparency, and beam propagation direction. Various types of electrically tunable diffractive optical elements utilizing active modulation of refractive index, geometrical shape, and bandgap have been discussed. Finally, this review concludes by proposing the integration of ultra-thin and light-weight diffractive optics presenting potential applications in micro-electronics, biomedical imaging, space exploration, and extended reality.

Selective thin-film removal is needed in many microfabrication processes such as 3-D patterning of optoelectronic devices and localized repairing of integrated circuits. Various wet or dry etching methods are available, but laser machining is a tool of green manufacturing as it can remove thin films by ablation without use of toxic chemicals. However, laser ablation causes thermal damage on neighboring patterns and underneath substrates, hindering its extensive use with high precision and integrity. Here, using ultrashort laser pulses of sub-picosecond duration, we demonstrate an ultrafast mechanism of laser ablation that leads to selective removal of a thin metal film with minimal damage on the substrate. The ultrafast laser ablation is accomplished with the insertion of a transition metal interlayer that offers high electron-phonon coupling to trigger vaporization in a picosecond timescale. This contained form of heat transfer permits lifting off the metal thin-film layer while blocking heat conduction to the substrate. Our ultrafast scheme of selective thin film removal is analytically validated using a two-temperature model of heat transfer between electrons and phonons in material. Further, experimental verification is made using 0.2 ps laser pulses by micropatterning metal films for various applications.