💡 The paper proposes a self supervised framework called Self Supervised Prompt Optimization that optimizes prompts for large language models without requiring external references. The problem addressed is that manually designed prompts require expertise and iterative experimentation, while existing prompt optimization methods rely heavily on external references such as ground truth or human evaluation, which can be costly to obtain. The proposed method derives evaluation and optimization signals purely from output comparisons, where a large language model evaluator selects superior prompts through pairwise output comparisons, and a large language model optimizer aligns outputs with task requirements. The results show that the proposed method outperforms state of the art prompt optimization methods, achieving comparable or superior results with significantly lower costs and fewer samples, demonstrating its effectiveness and efficiency. The method can optimize prompts for both closed and open ended tasks, and can be applied in real world scenarios where external references are unavailable or costly to obtain.