Since the groundbreaking discovery of bacteria by Antonie van Leeuwenhoek in the late 17th century, scientists have been striving to uncover the secrets of the microscopic world. However, traditional optical methods have their limitations, specifically the diffraction limit. This limit arises from the wave nature of light and prevents us from obtaining a focused image smaller than half the wavelength of the light used for observation. Previous attempts at overcoming this limit with “super lenses” have been unsuccessful due to extreme visual losses, making the lenses opaque. Excitingly, physicists at the University of Sydney have now presented a unique and innovative solution to achieve superlensing with minimal losses, breaking through the diffraction limit by nearly four times.
In their recent work published in Nature Communications, the researchers from the University of Sydney have successfully demonstrated a new pathway to superlensing without the need for a super lens. The key to their success lies in removing the physical lens altogether. Lead author of the research, Dr. Alessandro Tuniz, explains, “We have now developed a practical way to implement superlensing, without a super lens. To do this, we placed our light probe far away from the object and collected both high- and low-resolution information. By measuring further away, the probe doesn’t interfere with the high-resolution data, a feature of previous methods.”
Previous attempts at creating super lenses involved using novel materials, but most of them suffered from excessive light absorption, rendering the lenses ineffective. Dr. Tuniz and his team, however, overcame this challenge by employing a unique post-processing technique on a computer. By performing the superlens operation after the measurement itself, they were able to selectively amplify evanescent (or vanishing) light waves, generating a “truthful” image of the object. This breakthrough paves the way for practical applications in various fields such as cancer diagnostics, medical imaging, archaeology, forensics, and beyond.
The researchers highlight several potential applications for their novel approach to superlensing. Co-author Associate Professor Boris Kuhlmey suggests that their method could enhance moisture content determination in leaves with greater resolution and enable advanced microfabrication techniques, including non-destructive assessment of microchip integrity. Importantly, their technique could also contribute to the analysis of artwork, aiding in the detection of art forgery or hidden layers. This innovative approach opens up new possibilities for the field of super-resolution microscopy and promises to revolutionize imaging technologies across various disciplines.
A common challenge in superlensing attempts has been maintaining the integrity of high-resolution information. Typically, researchers focused on closely examining this valuable data, as it decays exponentially with distance, while low-resolution data persists. Unfortunately, moving the probe too close to the object can distort the resulting image. Associate Professor Kuhlmey explains their approach, stating, “By moving our probe further away, we can maintain the integrity of the high-resolution information and use a post-observation technique to filter out the low-resolution data.” This strategic adjustment ensures that the true essence of the object is preserved while eliminating unwanted visual noise.
The experiments conducted by the University of Sydney researchers utilized light at the terahertz frequency with a millimeter wavelength, falling within the spectrum between visible and microwave regions. Associate Professor Kuhlmey emphasizes the challenges of working within this frequency range but also highlights the exciting opportunities it presents. He suggests that valuable information about biological samples, such as protein structure and hydration dynamics, could be obtained in this range. Additionally, the method may find applications in cancer imaging, further enhancing our ability to study and understand this complex disease.
The University of Sydney’s breakthrough in breaking through the diffraction limit opens up a new era of superlensing without the need for physically opaque super lenses. This new approach allows for high-resolution imaging while maintaining a safe distance from the object, minimizing distortion. The potential applications of this technique in various fields, ranging from medical diagnostics to art analysis, are abundant. As researchers continue to refine and expand upon this novel method, we can expect significant advancements in imaging technologies, bringing the microscopic world into focus like never before.