Nanoparticle-Based Biophotonics in 2025: Unleashing Precision Imaging and Next-Gen Diagnostics. Explore How Nanotechnology is Transforming Biophotonics and Shaping the Future of Healthcare and Research.

• Executive Summary: Key Trends and Market Drivers in 2025
• Market Size, Growth Forecast (2025–2029), and CAGR Analysis
• Core Nanoparticle Technologies in Biophotonics
• Major Applications: Imaging, Sensing, and Therapeutics
• Leading Companies and Industry Initiatives (e.g., thermofisher.com, zeiss.com, olympus-lifescience.com)
• Regulatory Landscape and Standards (e.g., ieee.org, fda.gov)
• Recent Breakthroughs in Nanoparticle Synthesis and Functionalization
• Challenges: Biocompatibility, Scalability, and Safety
• Investment, Funding, and Partnership Trends
• Future Outlook: Emerging Opportunities and Strategic Recommendations
• Sources & References

Executive Summary: Key Trends and Market Drivers in 2025

Nanoparticle-based biophotonics is poised for significant growth in 2025, driven by rapid advancements in nanomaterial engineering, increasing demand for precision diagnostics, and the expanding adoption of photonic technologies in biomedical applications. The convergence of nanotechnology and photonics is enabling the development of highly sensitive, multiplexed, and minimally invasive tools for imaging, sensing, and therapy. This section highlights the key trends and market drivers shaping the sector in 2025 and the near future.

A primary trend is the integration of engineered nanoparticles—such as gold, silver, silica, and quantum dots—into biophotonic platforms for enhanced imaging and biosensing. These nanoparticles offer unique optical properties, including tunable surface plasmon resonance and strong fluorescence, which are being harnessed to improve the sensitivity and specificity of diagnostic assays. Companies like Thermo Fisher Scientific and Sigma-Aldrich (now part of Merck KGaA) are at the forefront, supplying a broad range of functionalized nanoparticles tailored for biophotonic research and clinical applications.

Another key driver is the growing clinical adoption of nanoparticle-based contrast agents for in vivo imaging modalities such as optical coherence tomography (OCT), photoacoustic imaging, and fluorescence-guided surgery. These agents enable real-time visualization of cellular and molecular processes, supporting earlier disease detection and more precise surgical interventions. Bruker Corporation and Olympus Corporation are notable for their advanced imaging systems that increasingly incorporate nanoparticle-enhanced technologies.

The market is also witnessing increased investment in the development of theranostic nanoparticles—multifunctional platforms that combine diagnostic and therapeutic capabilities. These innovations are being propelled by collaborations between nanomaterial suppliers, medical device manufacturers, and academic research centers. For example, nanoComposix (a Fortis Life Sciences company) specializes in custom nanoparticle synthesis for both research and commercial biophotonic applications, supporting the translation of laboratory breakthroughs into clinical products.

Regulatory momentum is another factor shaping the landscape. Agencies are updating guidelines to address the unique safety and efficacy considerations of nanoparticle-enabled biophotonic devices, which is expected to streamline the path to market for new products in the coming years. As a result, the sector is likely to see accelerated commercialization and broader clinical adoption through 2025 and beyond.

In summary, the nanoparticle-based biophotonics market in 2025 is characterized by technological innovation, expanding clinical utility, and a robust ecosystem of suppliers and device manufacturers. These trends are expected to drive continued growth and diversification of applications, particularly in precision diagnostics, image-guided therapy, and personalized medicine.

Market Size, Growth Forecast (2025–2029), and CAGR Analysis

The global market for nanoparticle-based biophotonics is poised for robust growth from 2025 through 2029, driven by rapid advancements in nanotechnology, increasing adoption of photonic diagnostics, and expanding applications in medical imaging, biosensing, and targeted therapy. Nanoparticle-based biophotonics leverages the unique optical properties of nanoparticles—such as gold, silver, silica, and quantum dots—to enhance sensitivity and specificity in biomedical applications. This sector is witnessing significant investments from both established industry leaders and innovative startups, reflecting its strategic importance in next-generation healthcare solutions.

As of 2025, the market is estimated to be valued in the low-to-mid single-digit billion USD range, with North America and Europe leading in adoption due to strong research infrastructure and early regulatory approvals. Asia-Pacific is expected to demonstrate the fastest growth, propelled by increasing healthcare expenditure and government initiatives supporting nanomedicine and photonics research. The compound annual growth rate (CAGR) for the nanoparticle-based biophotonics market is projected to be in the range of 12% to 15% over the 2025–2029 period, outpacing the broader biophotonics sector due to the accelerating integration of nanomaterials in clinical and research settings.

Key industry players are actively expanding their nanoparticle-enabled product portfolios. Thermo Fisher Scientific and PerkinElmer are notable for their advanced nanoparticle-based imaging reagents and biosensing platforms, which are widely used in both preclinical and clinical research. Carl Zeiss AG continues to innovate in optical instrumentation, integrating nanoparticle technologies for enhanced microscopy and diagnostic imaging. Meanwhile, Oxford Instruments is advancing nanoparticle characterization tools, supporting quality control and regulatory compliance for biophotonic applications.

Emerging companies are also making significant contributions. nanoComposix (a Fortis Life Sciences company) specializes in custom nanoparticles for biosensing and imaging, while Creative Diagnostics offers a broad range of nanoparticle conjugates for research and diagnostic use. These companies are fostering innovation by enabling tailored solutions for specific biophotonic applications, such as multiplexed assays and real-time in vivo imaging.

Looking ahead, the market outlook remains highly positive, with anticipated breakthroughs in nanoparticle engineering, regulatory harmonization, and integration with artificial intelligence for data analysis. Strategic collaborations between industry, academia, and healthcare providers are expected to accelerate commercialization and clinical translation. As a result, nanoparticle-based biophotonics is set to play a pivotal role in precision medicine, early disease detection, and minimally invasive therapies through 2029 and beyond.

Core Nanoparticle Technologies in Biophotonics

Nanoparticle-based biophotonics is rapidly advancing, driven by the convergence of nanotechnology and photonic engineering to enable highly sensitive, multiplexed, and minimally invasive biomedical applications. In 2025, the field is characterized by the deployment of core nanoparticle technologies such as quantum dots, gold nanoparticles, upconversion nanoparticles, and silica-based nanostructures, each offering unique optical properties for imaging, diagnostics, and therapeutic interventions.

Quantum dots (QDs), semiconductor nanocrystals with size-tunable fluorescence, remain at the forefront for in vitro and in vivo imaging due to their high brightness and photostability. Companies like Thermo Fisher Scientific and Sigma-Aldrich (a subsidiary of Merck KGaA) continue to expand their portfolios of QDs with improved biocompatibility and emission profiles tailored for multiplexed detection in clinical assays and live-cell imaging. Recent product lines focus on cadmium-free QDs to address toxicity concerns, aligning with regulatory trends and clinical translation efforts.

Gold nanoparticles (AuNPs) are another cornerstone, valued for their strong surface plasmon resonance and ease of functionalization. In 2025, AuNPs are widely used in photothermal therapy, biosensing, and as contrast agents in optical coherence tomography. BBI Solutions and nanoComposix (now part of Fortis Life Sciences) are prominent suppliers, offering highly uniform AuNPs with customizable surface chemistries for targeted delivery and enhanced signal amplification in lateral flow assays and point-of-care diagnostics.

Upconversion nanoparticles (UCNPs), which convert near-infrared (NIR) light to visible emission, are gaining traction for deep-tissue imaging and photodynamic therapy. Their ability to minimize background autofluorescence and enable excitation at tissue-penetrating wavelengths is being leveraged by companies such as Creative Diagnostics, which provides UCNPs for research and preclinical applications. Ongoing developments focus on improving quantum efficiency and surface modification for targeted imaging and drug delivery.

Silica nanoparticles, often used as carriers for fluorescent dyes or as scaffolds for hybrid nanostructures, are integral to multiplexed bioassays and super-resolution imaging. Cytodiagnostics and Merck KGaA supply a range of silica-based nanoparticles with tunable porosity and surface functionalities, supporting the integration of multiple photonic modalities in a single platform.

Looking ahead, the next few years are expected to see further integration of these core nanoparticle technologies with advanced photonic systems, including miniaturized light sources and detectors, to enable real-time, point-of-care diagnostics and image-guided therapies. The emphasis on biocompatibility, scalability, and regulatory compliance will drive innovation, with industry leaders and emerging startups alike contributing to the translation of nanoparticle-based biophotonics from research to clinical practice.

Major Applications: Imaging, Sensing, and Therapeutics

Nanoparticle-based biophotonics is rapidly advancing, with 2025 poised to see significant developments in imaging, sensing, and therapeutics. The integration of engineered nanoparticles with photonic technologies is enabling unprecedented sensitivity, specificity, and multifunctionality in biomedical applications.

In imaging, nanoparticles such as quantum dots, gold nanorods, and upconversion nanoparticles are being utilized for their unique optical properties, including tunable emission wavelengths and high photostability. These features are driving the adoption of nanoparticle-based contrast agents in fluorescence and photoacoustic imaging. For example, Thermo Fisher Scientific continues to expand its portfolio of quantum dot reagents for multiplexed imaging in both preclinical and clinical research. Similarly, nanoComposix, a subsidiary of Fisher Scientific, is supplying gold and silica nanoparticles tailored for optical imaging and biosensing applications.

In biosensing, nanoparticles are being integrated into photonic sensor platforms to enhance detection limits for biomarkers and pathogens. Plasmonic nanoparticles, particularly gold and silver, are central to surface-enhanced Raman scattering (SERS) sensors, which are being commercialized for rapid diagnostics. Companies like Creative Diagnostics and Sigma-Aldrich (now part of Merck KGaA) are providing a range of functionalized nanoparticles for research and development in this area. The trend toward point-of-care diagnostics is expected to accelerate, with nanoparticle-based photonic sensors enabling real-time, ultrasensitive detection in compact formats.

Therapeutically, nanoparticle-based biophotonics is making strides in photothermal and photodynamic therapies. Gold nanoshells and nanorods, when activated by near-infrared light, can selectively ablate tumor tissues with minimal damage to surrounding healthy cells. Nanospectra Biosciences is advancing clinical trials of its AuroShell® technology, which leverages gold-silica nanoparticles for targeted photothermal ablation of solid tumors. Additionally, upconversion nanoparticles are being explored for deep-tissue photodynamic therapy, with ongoing collaborations between academic groups and industry to optimize their safety and efficacy.

Looking ahead, the next few years are expected to bring further convergence of nanotechnology and photonics, with a focus on multifunctional platforms that combine imaging, sensing, and therapy. Regulatory progress and standardization efforts, led by organizations such as ISO, will be crucial for clinical translation. As manufacturing capabilities scale and new surface chemistries are developed, nanoparticle-based biophotonics is set to play a transformative role in precision medicine and point-of-care healthcare.

Leading Companies and Industry Initiatives (e.g., thermofisher.com, zeiss.com, olympus-lifescience.com)

The field of nanoparticle-based biophotonics is rapidly advancing, with several leading companies and industry initiatives shaping its trajectory in 2025 and the coming years. These organizations are driving innovation in the synthesis, functionalization, and application of nanoparticles for imaging, diagnostics, and therapeutic interventions, leveraging their expertise in photonics, nanotechnology, and life sciences.

A key player in this sector is Thermo Fisher Scientific, which offers a broad portfolio of nanoparticles, quantum dots, and fluorescent probes tailored for biophotonic applications. Their products are widely used in advanced imaging, flow cytometry, and biosensing, supporting both research and clinical workflows. In 2025, Thermo Fisher continues to expand its range of surface-modified nanoparticles, enabling more precise targeting and multiplexed detection in biological systems.

Another major contributor is Carl Zeiss AG, renowned for its high-resolution optical systems and microscopes. Zeiss integrates nanoparticle-based contrast agents into its imaging platforms, enhancing sensitivity and specificity in cellular and tissue-level visualization. The company is actively collaborating with academic and industrial partners to develop next-generation biophotonic tools that exploit the unique optical properties of engineered nanoparticles.

Olympus Corporation is also at the forefront, providing advanced microscopy solutions compatible with nanoparticle-based probes. Olympus’s systems are optimized for super-resolution and live-cell imaging, supporting the visualization of nanoparticle interactions in real time. Their ongoing initiatives include partnerships with nanomaterial suppliers to ensure seamless integration of novel probes into their imaging workflows.

In the realm of nanoparticle synthesis and functionalization, Sigma-Aldrich (Merck KGaA) remains a significant supplier, offering a diverse catalog of gold, silver, silica, and magnetic nanoparticles for biophotonic research. Their materials are widely adopted in the development of biosensors, photothermal therapies, and multiplexed assays, with a focus on reproducibility and biocompatibility.

Looking ahead, industry initiatives are increasingly focused on standardization, regulatory compliance, and translational research. Organizations such as International Organization for Standardization (ISO) are working with industry stakeholders to establish guidelines for nanoparticle characterization and safety in biophotonic applications. Collaborative efforts between manufacturers, instrument developers, and regulatory bodies are expected to accelerate the clinical adoption of nanoparticle-based biophotonics, particularly in precision diagnostics and targeted therapies.

As the sector matures, the interplay between leading companies and industry initiatives will be crucial in overcoming technical and regulatory challenges, ensuring that nanoparticle-based biophotonics continues to deliver transformative solutions in biomedical science and healthcare.

Regulatory Landscape and Standards (e.g., ieee.org, fda.gov)

The regulatory landscape for nanoparticle-based biophotonics is rapidly evolving as these technologies transition from research laboratories to clinical and commercial applications. In 2025, regulatory agencies and standards organizations are intensifying their focus on the unique challenges posed by the integration of nanoparticles with photonic systems for biomedical use. The U.S. Food and Drug Administration (FDA) continues to play a central role in the oversight of medical devices and diagnostics that incorporate nanomaterials, emphasizing the need for robust safety, efficacy, and quality data. The FDA’s Center for Devices and Radiological Health (CDRH) has issued guidance documents addressing the characterization, biocompatibility, and risk assessment of nanomaterials in medical devices, with particular attention to their interaction with light and biological tissues.

In parallel, international standards bodies such as the International Electrotechnical Commission (IEC) and the International Organization for Standardization (ISO) are updating and expanding standards relevant to biophotonics and nanotechnology. ISO’s Technical Committee 229 (Nanotechnologies) and IEC’s Technical Committee 76 (Optical Radiation Safety and Laser Equipment) are collaborating to harmonize definitions, testing protocols, and safety requirements for devices that combine nanoparticles and photonic elements. These efforts aim to facilitate global market access and ensure consistent safety benchmarks.

The Institute of Electrical and Electronics Engineers (IEEE) is also active in this space, with working groups developing standards for optical imaging, biosensing, and photonic device interoperability. In 2025, IEEE is expected to release new guidelines addressing the integration of nanomaterials in photonic circuits and biosensors, reflecting the growing commercial interest in these hybrid technologies.

Manufacturers and developers, such as Thermo Fisher Scientific and Olympus Corporation, are increasingly engaging with regulators and standards bodies to ensure their nanoparticle-based biophotonic products meet evolving requirements. These companies are investing in advanced characterization and quality control systems to comply with regulatory expectations, particularly regarding nanoparticle size distribution, surface chemistry, and photostability.

Looking ahead, the regulatory outlook for nanoparticle-based biophotonics will likely involve more rigorous premarket evaluation, post-market surveillance, and harmonization of international standards. As the field matures, agencies such as the FDA, IEC, ISO, and IEEE are expected to issue further guidance and standards, supporting innovation while safeguarding patient safety and public health.

Recent Breakthroughs in Nanoparticle Synthesis and Functionalization

The field of nanoparticle-based biophotonics has witnessed significant advancements in synthesis and functionalization techniques, particularly as the demand for highly specific, biocompatible, and multifunctional nanoparticles accelerates in 2025. Recent breakthroughs have focused on improving the precision, scalability, and reproducibility of nanoparticle production, as well as enabling more sophisticated surface modifications to enhance their performance in imaging, diagnostics, and therapeutic applications.

A major trend in 2024–2025 is the adoption of continuous flow synthesis methods, which offer superior control over particle size distribution and surface chemistry compared to traditional batch processes. Companies such as MilliporeSigma (the U.S. and Canada life science business of Merck KGaA) have expanded their portfolios to include advanced nanoparticle synthesis kits and reagents, supporting both academic and industrial research. These kits enable the rapid and reproducible fabrication of gold, silver, and silica nanoparticles with tunable optical properties, which are critical for biophotonic applications such as surface-enhanced Raman scattering (SERS) and fluorescence imaging.

Surface functionalization remains a key area of innovation. In 2025, there is a growing emphasis on bio-orthogonal and click chemistry approaches, allowing for the attachment of targeting ligands, antibodies, or therapeutic agents with high specificity and minimal off-target effects. Thermo Fisher Scientific has introduced new lines of functionalized nanoparticles, including quantum dots and upconversion nanoparticles, with customizable surface coatings for targeted imaging and multiplexed detection. These advances are enabling more sensitive and selective detection of biomarkers in complex biological environments.

Another notable development is the integration of artificial intelligence (AI) and machine learning in nanoparticle design and synthesis optimization. Companies like Bruker Corporation, known for their advanced analytical instrumentation, are collaborating with research institutions to develop AI-driven platforms that predict optimal synthesis parameters and functionalization strategies, accelerating the translation of novel nanoparticles from the lab to clinical and industrial settings.

Looking ahead, the outlook for nanoparticle-based biophotonics is robust, with ongoing investments in scalable manufacturing and regulatory-compliant production. Industry leaders such as nanoComposix (now part of Fortis Life Sciences) are expanding their GMP-compliant nanoparticle manufacturing capabilities to meet the stringent requirements of clinical diagnostics and therapeutics. As these technologies mature, the next few years are expected to bring further integration of multifunctional nanoparticles into commercial biophotonic platforms, driving advances in early disease detection, image-guided therapy, and personalized medicine.

Challenges: Biocompatibility, Scalability, and Safety

Nanoparticle-based biophotonics is rapidly advancing, but several critical challenges remain in 2025, particularly regarding biocompatibility, scalability, and safety. As these technologies move closer to clinical and commercial applications, addressing these issues is essential for widespread adoption.

Biocompatibility is a primary concern, as nanoparticles interact intimately with biological systems. Surface chemistry, size, and shape all influence cellular uptake, immune response, and toxicity. Companies such as Thermo Fisher Scientific and Sigma-Aldrich (now part of Merck KGaA) are actively developing surface modification techniques—such as PEGylation and biomolecule conjugation—to improve nanoparticle stability and reduce immunogenicity. However, long-term in vivo studies remain limited, and regulatory agencies are calling for more comprehensive data on chronic exposure and biodistribution.

Scalability is another significant hurdle. While laboratory-scale synthesis of nanoparticles with precise optical properties is well established, translating these methods to industrial-scale production without compromising quality or reproducibility is challenging. nanoComposix (a Fortis Life Sciences company) and Avantor are among the few suppliers offering GMP-grade nanoparticles for biophotonic applications, but batch-to-batch consistency and cost-effectiveness remain ongoing concerns. Automation and continuous flow synthesis are being explored to address these issues, but widespread implementation is still in its early stages.

Safety is closely linked to both biocompatibility and scalability. Regulatory bodies such as the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) are increasing scrutiny of nanoparticle-based products, requiring detailed toxicological profiles and standardized characterization protocols. Companies like Bruker are providing advanced analytical tools for nanoparticle characterization, supporting compliance with evolving regulatory standards. However, the lack of harmonized international guidelines for nanoparticle safety assessment continues to slow clinical translation.

Looking ahead, the next few years are expected to see increased collaboration between industry, academia, and regulatory agencies to develop standardized protocols for nanoparticle synthesis, characterization, and safety evaluation. The formation of consortia and public-private partnerships is likely to accelerate the establishment of best practices, paving the way for safer and more scalable biophotonic technologies. As the field matures, addressing these challenges will be crucial for realizing the full potential of nanoparticle-based biophotonics in diagnostics, imaging, and therapy.

Investment, Funding, and Partnership Trends

The landscape of investment, funding, and partnerships in nanoparticle-based biophotonics is experiencing significant momentum as of 2025, driven by the convergence of nanotechnology and photonics for advanced biomedical applications. The sector is attracting capital from both established industry leaders and venture-backed startups, with a focus on diagnostics, imaging, and targeted therapeutics.

Major corporations with established nanomaterials and photonics portfolios, such as Thermo Fisher Scientific and Olympus Corporation, continue to expand their investments in nanoparticle-enabled imaging and detection platforms. These companies are leveraging their global R&D infrastructure to accelerate the commercialization of quantum dot and gold nanoparticle-based biosensors, as well as advanced fluorescence imaging systems. Thermo Fisher Scientific has notably increased its collaborative research agreements with academic institutions and biotech firms to co-develop next-generation nanoparticle reagents for clinical and research use.

Startups and scale-ups are also playing a pivotal role. Companies such as nanoComposix (now part of Fortis Life Sciences) and Creative Diagnostics are attracting venture capital and strategic investments to expand their nanoparticle synthesis and functionalization capabilities. These firms are frequently entering into partnerships with medical device manufacturers and pharmaceutical companies to integrate their nanomaterials into biophotonic diagnostic kits and point-of-care devices.

Public-private partnerships and government funding initiatives are further catalyzing growth. In the United States, the National Nanotechnology Initiative (NNI) continues to support translational research and commercialization efforts in biophotonics, with a focus on nanoparticle-based imaging agents and biosensors. European consortia, often involving members such as Siemens Healthineers and leading academic centers, are channeling Horizon Europe funds into collaborative projects targeting early cancer detection and minimally invasive diagnostics using nanoparticle-enhanced photonic technologies.

Looking ahead, the next few years are expected to see an increase in cross-sector alliances, particularly between nanomaterial suppliers, photonics hardware manufacturers, and digital health companies. The growing demand for multiplexed, real-time biosensing and image-guided therapies is likely to drive further investment from both corporate venture arms and institutional investors. As regulatory pathways for nanoparticle-enabled biophotonic devices become clearer, the sector is poised for accelerated product launches and expanded clinical adoption, reinforcing its status as a focal point for innovation and capital inflow in the life sciences.

Future Outlook: Emerging Opportunities and Strategic Recommendations

The future of nanoparticle-based biophotonics is poised for significant advancements and market expansion through 2025 and the following years, driven by rapid innovation in nanomaterials, photonic device integration, and clinical translation. As the demand for highly sensitive, non-invasive diagnostic and therapeutic tools grows, the convergence of nanotechnology and photonics is expected to unlock new frontiers in biomedical imaging, targeted drug delivery, and biosensing.

Key industry players are intensifying their focus on the development of multifunctional nanoparticles with tunable optical properties, such as gold nanorods, quantum dots, and upconversion nanoparticles. These materials are being engineered for enhanced biocompatibility, stability, and specificity, enabling real-time imaging and photothermal or photodynamic therapies. For instance, Thermo Fisher Scientific continues to expand its portfolio of fluorescent and plasmonic nanoparticles for research and clinical applications, while Sigma-Aldrich (now part of Merck KGaA) supplies a broad range of nanomaterials tailored for biophotonic research.

In 2025, the integration of nanoparticles with advanced photonic platforms—such as fiber-optic probes, microfluidic chips, and wearable sensors—is expected to accelerate. Companies like Hamamatsu Photonics are advancing photodetector and imaging technologies that synergize with nanoparticle-based contrast agents, supporting the development of next-generation point-of-care diagnostics and intraoperative imaging systems. Meanwhile, Carl Zeiss AG is leveraging its expertise in optical instrumentation to enable high-resolution visualization of nanoparticle-labeled biomolecules in clinical and research settings.

Strategically, stakeholders are advised to prioritize collaborations between nanomaterial manufacturers, photonics companies, and healthcare providers to streamline regulatory approval and clinical adoption. The growing emphasis on personalized medicine and minimally invasive procedures is likely to drive demand for nanoparticle-enabled photonic solutions that offer multiplexed detection and targeted therapy with minimal side effects.

Looking ahead, emerging opportunities include the development of biodegradable and stimuli-responsive nanoparticles for controlled drug release, as well as the use of artificial intelligence to analyze complex biophotonic data. Regulatory agencies are expected to refine guidelines for the safe use of nanomaterials in medical devices, further supporting market growth. Companies investing in scalable manufacturing, robust quality control, and interdisciplinary R&D are well-positioned to capitalize on the expanding landscape of nanoparticle-based biophotonics through 2025 and beyond.

Sources & References

• Thermo Fisher Scientific
• Bruker Corporation
• Olympus Corporation
• PerkinElmer
• Carl Zeiss AG
• Oxford Instruments
• Creative Diagnostics
• Fisher Scientific
• Nanospectra Biosciences
• ISO
• Olympus Corporation
• IEEE
• Avantor
• Siemens Healthineers
• Hamamatsu Photonics